With modern firearms there is no problem dry firing the weapon repeatedly. Just doing it to relax the hammer spring when you store the rifle is not going to hurt it at all. Just make SURE that it's not loaded. Safety first.

As for the camo... most current factory camo is dipped, which basically covers it with a thin film of camo patterned plastic. As long as the film is not damaged (scratched through to bare metal), then the metal is sealed and all it needs is just to be wiped clean after use. If the camo film is damaged, then the bare metal underneath becomes vulnerable to the elements, and should be treated with a preservative just like a non-camo gun.

Mike