Saad,
I use a Birch Wood Casey, Super Blue that I purchase at WalMart. I'm sure there's better products but I've found this works well.
Here's exactly what I do:
1. Don't remove the old finish, just any rust spots that you can see and feel when you run your finger tips over the barrels.
2. I beleive that the bluing chemical reacts with the original rust bluing and turns it black again (one of the things that happens with age is the original rust bluing turns brown), as well as bluing any areas where the original finish has been removed. Anyhow, it'll turn the entire barrel a nice dark blue again, just don't polish it down to bare steel.
3. I use automotive starting fluid (ether) as a degreaser. It degreases well and drys very fast, but nearly any good solvent should work well as a degreaser.
4. after cleaning any surface rust patches off the barrel and getting it smooth to the touch, I take a rag and soak it in the bluing compound and rub down the barrels, rinsing, degreasing and then repeating several times until the barrel has a nice evenly blued finish. Make sure you wash all the bluing off when you finish, it's a very powerful corrosive and will pit the barrel if left on too long (just follow directions on the product).
Steve
