The best advice I can give is practice, practice, practice. Covering is a task that can't be adequately described in print, and even with visual aids, you still won't get the "feel" without doing it for yourself.

One thing you do NOT want to do is just lay the covering over the area you want to cover like a sheet, tack the edges, then shrink. Always heat, stretch, then lay down. With practice, you can get good enough to lay the covering down drum tight and smooth without using a heat gun.