I haven't tried rustoleum camo paint so I can't comment on that, but I'd recommend Krylon Camo paint for sure.
Consider only painting the parts of your gun you want painted, so some disassembly may be required. Take extra time and care taping off anything you don't want painted or shouldn't get paint in it.
Use some netting or large grass/leaves or whatever to give the paint job a design. Do several, even overlapping coats to give it a good texture.
After I'd coat it in a few layers of a protectant, such as Krylon make-it-stone.
If you're painting the whole gun, do a super careful, really good job of taping up stuff. I mean always put effort into your taping, but you know what I mean.
When I painted mine, started with three solid layers of tan, then several overlapping layers of tan and green, then three solid layers of make it stone.
ďREALITY IS LIKE A STONE. TO MANY ITíS HARD AND COLD, THEY CANíT HUG IT OR EAT IT, IT ONLY FRUSTERATES THEM AND DOESNíT DO THEM MUCH GOOD. TO OTHERS ITíS STRONG AND DEPENDABLE, YOU CAN BUILD WITH IT, BUILD UPON IT, OR WORK WITH IT, ALSO USE IT TO SMASH PEOPLE IN THE FACE.Ē