I've been doing what you described for almost 25 years and it has never let me down. However, I never saw the need to glue the toothpicks in since the surface is going to be covered. This makes life a lot easier if I ever needed to remove that surface.

The hole I drill for the toothpicks is relatively small so the toothpick really needs to be pushed in there. Also, if in doubt, you can always use two toothpicks per side (4 for each hinge).

Damon