Durability is in the prep work.
Take your time. 3 or 4 light coats are better than 1 heavy coat. You MUST scuff sand all parts to be painted with no less than 320 grit. You must degrease all parts before paint is applied.
1- Disassemble parts to be painted (if possible)
2- Scuff sand with 320 grit
3- Wash your hands with common dish soap (great degreaser)
4- Wash and rinse all parts with hot water using dish soap (parts will dry faster and again dish soap is a great degreaser)
5- Hang parts to be painted in a clean place free of dirt and dust
6- Spray a light coat of paint and let it dry fully (no primer needed)
7- Apply 2-3 more coats just a bit heavier than the first (these can be applied about 15 min appart in the case of Krylon Camo paints)
8- Allow to fully dry before handling (3-5 hours)
I have yet to have ANY problems using Krylon Camo paints using this method and I have painted alot of parts and guns with it. You will only run into problems if the parts were previously painted with another paint, in this case you will have to remove as much old paint as possible and prime with a Krylon primer and allow to fully dry before applying your paint.
One of many I have painted:
