I don't think any paint is really going to stick to the rubber, so my advice is to mask off the rubber portions. Even if it does stick at first, the moment it touches anything and flexes it will flake.
As for the plastic and metal parts, Krylon Camo works great, and I've done several guns with it in the past. You just want to make sure you completely disassemble the gun, clean all the parts with a degreaser soap like fast orange or liquid pumice, rinse thoroughly, dry completely, then spray evenly and thinly and do at least two coats.
The real key is to let it completely cure, not just wait until it's dry enough to handle. I'm talking let the parts sit untouched for a good week in a room temperature, dry environment. If you give it a whole week all of the thinner in the paint has time to evaporate out and it becomes VERY resilient. If you only wait a couple of hours before screwing around with it you wind up with problems and flaking down the road.
Jay AKA Rogue...
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