Step 1: Materials
A nerf gun (of your choice, but again i will be using a Maverick)
Some plastic spray paint (krylon fusion plastic works well) one can of black and any number of other colors you want to use.
An exacto knife
some general purpose sand paper (or low grit if you want to minimize the risk of making scratches the paint wont cover)
some blue painting tape
a small philips head screw driver (I refer to these as tweakers)
and a cardboard surface for painting on top of (a grassy gun is no fun and mom probably wont be happy if you paint her driveway)