SE... You will not have to go to all that trouble to restore the finish on your 870 Express.. Since you have no pitting, simply rough up the finish a little with a scotch brite pad then you can spray over with DuraCoat. Matte black will restore your finish and last forever. Although parkerizing is a good "added" step, in your case, it's not needed. The Express shotgun already has a rough surface finish that provides your base for the DuraCoat. You can accomplish this on your own for less than $50.