Am looking to blue a gun at home. I don't feel it is worth having it done by a gunsmith due to cost and have been looking at Tetra and Birchwood Casey products. Has anyone used either of these or any others that you consider good quality and easy to use? Also, what kind of preparation is necessary for the existing finish? No scratches are present other than what I would call streaks in the existing blue finish that will not come out. I just want a nice smooth finish that will look good and last. Thanks for the help. Barn.