This is what I do for painting handles on swords/knives or pistol grips on guns:
1. Prime the area by swabbing with acetone/nail polish remover on a Q-tip.
2. Paint the area.
3. After the paint is dry, go over the painted area with brush-on Glue lightly.
4. Allow to cure at least 30 minutes.
5. Repeat steps 2-4.
Be sure that the hands of the figure you use to hold painted handles for aren't too tight that you have to force it to fit. This can be rectified by using a little sandpaper on the hands.
This technique can also be applied when painting other accessories like backpacks.
Hope this helps...
The last of a dying breed. ARAH 'til Death!