Ernest, I don't think a baked on coating would help. First, most "dry" coatings contain either carbon or graphite. Both are conductors which would kinda' pre-foul your plugs. Second, at combustion pressure and temp they would burn off anyway. The ceramic surface of the plug is the best thing that manufacturers could come up with that would tolerate the environment and cost less that $100.00 each!
Bill Jepson