Take the barrelled action out of the stock, wipe it down with alcohol to remove any oil on the bbl and action. Use masking tape to close off any area you don't want to paint (like the trigger opening, the bolt raceway etc.) and spray paint it with a primer layer. Then you can use camo paint found at Wally World in the paint section to camo it as you want.
Should you ever want to remove the paint, just use any normal paint remover, wipe the metal down with an oily cloth and you are back to square one.
I have done this many times and never had any problems with accuracy or removal.