1. Use silicon carbide paper up to 320 grit to prepare the steel. If a matte finish is desired then sand/bead blast the parts. Make sure all active rust is removed. You may need to use a commercial rust remover to assist in de-rusting heavily corroded parts.
2. Degrease with 3 washes of naptha or acetone. Then give it a bath in a warm solution of Dawn Dishwashing Detergent. Rinse thoroughly with hot water. Look for “sheeting” of the water on the steel and no beading. Beading means there is still oil on the surface. You don’t want any oil on it!
3. Generally, parts not coated with Rust Blue won’t rust in the blueing process. But if you desire added protection, spray any parts you don’t want to rust with clear lacquer. You can even coat the inside of the bore with it. It removes easily when you are through with lacquer thinner.