Paint removal is a real challenge! I have had some luck with soda blasting using high pressure, at least 80psi constant but it can still be tough to get paint off. There is a commercial stripper available for removing powder coatings that I have bought from Eastwood Automotive, it will remove anything but the fumes are terrible and I would finish it with soda blasting.
I did clean a Ducati bevel twin motor once, out of the frame and I sealed over any openings with silicone left to dry for a couple days. I then used fine glass bead at high pressure followed by soda blast to soften up the surface sheen left by the glass.
Before

After
