hmb, you are right, it doesn't just rub off, it wears off, very quickly and turns into a transparent gray. . It is an exercise in futility regardless of preparation. The way I do it is to bead blast the part then heat it in the oven to 300 degrees. Apply the cold blue until the part cools then card it with oil. Looks great if it's just for lookin at. I have had best results with Brownell's Oxpho blue. 44-40 will rust for days afterward, so it has to be rubbed with oil daily for a while. If cold blue worked no one would bother with hot blue.