Assuming it is possible for your dad to balance on LTE, counteracting is probably the movement that is lacking. But you should confirm he can balance if you haven't already. On a green slope, have him stand with his skis parallel to the fall line, move his hips to face his zipper down the hill, and then try to remain in balance while balancing on the LTE of the uphill ski and lifting the downhill ski. Pole tips should be in the air, if possible. Observe whether he can balance on both LTEs. Then have him do a gentle traverse while balancing on the LTE of the uphill ski and lifting the downhill ski. He'll need to face his zipper down the hill while doing this. As with all drills, make sure he looks up the hill for traffic before starting. Have him do this on both LTEs. If he has trouble balancing, he may need some boot adjustments before he will have success with the movements.
If he can balance, watch what is happening with the upper body during transition. If he is using any kind of upper body rotation to start the turn, he won't be able to hold his LTE. Have him start by doing half turns on a gentle slope (step tips straight down the fall line and then phantom move finish to a stop). While the turn is progressing, have him drag his inside (same side as the free, or lifted foot, same side as the direction of the turn) pole tip on the snow and push it forward. The goal is that as he rides his skis to a stop, the inside pole tip should be positioned directly above the inside ski tip. He should also see an arc in the snow corresponding to the path of the dragged pole--which means he has to push hard to make this happen. In addition to having the inside pole tip above the inside ski tip, his outside pole tip should be anywhere from directly below the heel piece of the outside ski to 45 degrees behind it. The latter is an exaggeration, but is a worthwhile target when developing CA. His zipper should be facing down the hill at the turn finish. His hips should be fully counteracted; i.e. he should have exhausted the range of motion that he has. Have him do several of these half turns to a stop in both directions and have him run through these cues and see if he is getting a good turn finish. He should get in the habit of checking off these cues whenever he comes to a stop. Once he has done a bunch of the half turns, have him link two turns, still pushing the inside hand, come to a stop and check his cues. Make sure he practices coming to a stop on both sides (which means starting from different sides). After doing several of those, have him ski a run focusing on pushing the inside pole. Once he gets comfortable with the inside pole push, he can try to add the Super Phantom transition back.
Like DougD suggested, Angry Mother is also a great drill for isolating CA. It can also help if his upper body rotation is caused by swinging his poles around.
Once you have eliminated any upper body rotation, if he is still having trouble with LTE balance, you can work into it by doing some LTE traverses where you just tap the tail of the downhill ski while balancing on the uphill ski. From there, instead of tapping the downhill ski, hold the lifted ski against the uphill boot for a moment (as if starting a Super Phantom). Then place it back down on the snow (instead of tipping). After a few traverses like that (and again, watch for traffic), you can build into a Super Phantom. Start on a gentle green slope and step tips facing the fall line. While holding himself with poles, have him establish balance on LTE, then release the poles to begin moving down the hill. Lift, touch and tilt the other (free) foot for a Phantom Move finish to a stop. Do a few of these in both directions. Then facing the fall line, have him step tips a step or two in one direction so he is no longer facing directly down the fall line. Repeat the process of establishing LTE (he'll need CA now--zipper down the hill), release the poles, and lift, touch, and tilt to a finish. After a few of these, keep stepping tips until the starting point is skis perpendicular to the fall line. At that point, he would be doing a stationary one-footed release. That may be too hard, but hopefully he was able to get some LTE engagement when the skis were just slightly off perpendicular and he had some movement. Like Max_501 suggested, the Wedge Blocker series is great and will have probably all of what I just described in it.
Ok, for you. Without seeing video, this is a guess on SMIM, but if you have a tail push, focus on flexing. Not only to release, but to engage. Somewhere in transition, you are extending in order to push tails. Boot-touch drills would be good for you, as would placing your poles across your thighs and attempting to keep them touching both thighs while you turn. (See this thread:
viewtopic.php?f=1&t=5278 for a picture of Harald demonstrating this drill). Another good drill would be doube pole drag, holding your hands below the grips. Make sure you keep both pole tips in the snow at all times. Pay attention to the uphill pole tip in transition--if the uphill tip comes off the snow, you extended.
Once you've done some work with flexing, work on releasing. On a moderate slope, start with skis across the hill, hold yourself on uphill LTE, zipper facing down the hill, then flatten the downhill ski. You are still holding yourself, but now you have one ski completely flat. Now you have to relax the uphill leg and let the up hill hip move downward and outward--meaning the hips move down the hill. This should cause the uphill ski to flatten and you should begin sliding sideways. Engage the uphill LTE to brake to a stop. Try this repeatedly from both sides. Then do the same thing, but once you start to slide, pull you feet back. The tips should begin to drop. Keep your feet held back and let the tips seek the fall line. Once you are pointed straight down the hill, Phantom Move finish to a stop. Repeat several times, both sides. The goal is to develop patience at the top of the turn. You don't need to be in a hurry to get your skis around. As long as the tips are above the fall line, you have plenty of time. From there, work into a stationary two footed release. If you can get that, try linking two footed releases. If the stationary two footed release seems too hard, try releasing from a traverse. In a gentle traverse, flex and tip the downhill ski (while relaxing the uphill hips and leg, just like a sideslip). As soon as the release happens and the tips seek the fall line, tip your uphill foot back towards the hill (letting the down hill foot follow the tipping) to bring the ski tips back up into the traverse. Repeat across the hill (watching out for traffic). If you can develop a release that doesn't involve a push, it is a relatively easy matter to continue through to engaging the new edges without a push. Once you begin flexing the old stance ski to trigger the release, just keep flexing it and tipping it into and throughout the duration of the new turn.