When I bought my kit from the previous owner, he had not removed any of the blue plastic film from any of the parts he had not worked on...except the roll bar frames (unless they came without it). Starting to do the prep work on these parts and I'm wondering about their condition. I've tried isopropyl alcohol and MEK and neither will touch it. When they're primed, I prep with alumiprep (actually, Bonderite C-IC 33 Aero). Will that be adequate prep for these parts or do they need something else?