Yep, just do it.
You can always sand it off and give it another go.
If you wish multicolor camo use some extra wide masking tape, the blue stuff, to mask an area after the base coat is applied.
Then mask an area of the stock and tear the tape to give rough edges to an opening in the tape. Paint it the second color. An so on......
If you don't go for jagged edges use an exacto type knife and cut the pattern you wish in the tape. If you are half way careful the tape may be cut with out cutting a groove in the stock.
Do all of this far away from people as the laughter and dumb questions may be a distraction.