First off, you may want to do some research on the 'Old Shot Gun' before you do anything to the orignal finish...
You never know what you have until you do the research!
I'd hate for someone to ruin the finish on a pre war Belgium Browning or a '97 Winchester!
Secondly, camo is the fad now, but you just don't know what's going to be 'Hot' next year...
You may want to stick with some of the removable camo tape.
You can go to green camo, to brown camo, to white camo as seasons change too.
Make people think you got a new gun for every season!