That Hotspot looks gorgeous in truck mode, painting the shutters was a good idea, and the black head is all sorts of toy nostalgia, might have to have a go at the Hasbro versions myself, especially since I have the Tomy version on preorder.
Hotspot is very nice! althought the hubcaps seems a bit too much "pimp my ride" the red trimming with the silver is not the kind of finish i'll expect on an emergency vehicule. The hoses, doors, and the tanks are nicely done. Have you considered adding him a silver face plate? like the GDO version
you sir have convinced me to at least repaint Hotspot's head, it just looks so sharp and gets nostalgia going since I had g1 Defensor when I was a kid
You might try disassembling them and soaking in some diluted Purple Power. Sounds like they have some of the mold release agent causing the paint to not adhere. Also try a thin layer of primer after soaking and rinsing - the Tamiya stuff works excellent. These repaints are making me jones to go get mine out of the display and get some repainting going - waiting on some parts first, though, so I only have to disassemble them once (arms for blades w/sleds, ratchets for the bodies, etc). They definitely look amazing now