Josh:
For the outside, simply draw file out the nasty pits, polish as best you can with wet-or-dry (wet) down to about 400 grit, then scour the whole set of barrels with "grey" Scotch Brite as sold by Brownells. Similar grits from local suppliers if you can find one. Then slather on Oxpho Blue per directions.

Go to any more effort and you'll make this gun a hobby -- not a shooter.

But it's good fun nonetheless.

Best, Kensal