Hand painting...not something I would want to do to my rifle. If I decide to cam up any of my firearms, this is the process I would use...

http://www.camo-solutions.com/dipping-process/

I am assuming you send your firearm off to these guys and it returns all nicely cammed up...but there are companies that will supply the materials for you to do it yourself at home.

Cheers, Cobbershot