I'm almost finished with a Twin Whistle painted diner. I'd like to do something with powders but the finish is so rough I think it might clunp up and ruin the paint job. The only thing I ever used dullcote on was plastic or metal. The pic won't show it well but the roof is like rough sawn lumber. Main concern is the roof. Could I seal it with something like Mod Podge. If it matters the paint is all acrylic.