A first time student - i've had 3 of those - the situation never came up because we worked in gentle traverse drills so that by the time they were going more down the fall line and actually doing a turn, they were already very comfortable with turning uphill to stop.
For an existing student that is using a braking or gliding wedge here is a link that may help:
http://www.harbskisystems.com/olg2.htm
Some people also call this drill the Phantom Drag
However, if they still don't have the basic basics of stepping or turning uphill to stop, they'll still might revert to that braking wedge to stop.
I'm not a cert anything, but just my thoughts on this for what it's worth.
I also work with people on sideslips (the PMTS way which is a bit different) so that they can create and control speed in a narrow situation without using the wedge.
Catwalks with a slight slope to the side are great for working on this with people and catwalks are another situation where students often will opt for a breaking wedge instead of the partial side slip alternative.