I tried it for the 1st time and rushed it a little bit, but it turned out okay I think. The rifle is a Marlin .22 LR that I never shoot.
I started by disassembling the rifle, masking it off where I didn't want paint, and priming it. Then I applied a tan base with Krylon special purpose camo tan. Once things were coated nicely I used butcher paper to make some freehand stencils and then sprayed them on with Krylon camo olive drab green. That's it.
Lessons learned:
1) If you're going to do it, make sure you take the time to do it right (i.e. letting the last coat dry before applying the next).
2) Use something stouter than butcher paper for stencils.
3) Practicing on something you don't care about before you camo something valuable is smart. Undoing spray-paint is a pain in the...