Grease is a lot better than paper for protecting the BB threads. Just spreads a layer in there, and wipe it off when done. Worked great for me, and now bleed like paper would allow.

For painting decals, paint the bike completely black, and let the paint dry completely. Then use painters tape to cover areas around the decal, as far out as you think paint may spray, and spray away. You can get some pretty neat designs if you're creative with the taping.