Resin ear pieces soft after brake fluid exposure

Hi there, I recently got my first resin Boba helmet which was painted the wrong way. The helmet has been wiped clean with DOT3 brake fluid, which worked really well. While working on the large main piece, the smaller parts had to be submerged fully to get the millimeter thick layer of coloured paint off of the primer layer. Unfortunately I got distracted and accidentally left them submerged overnight to discover my mistake in the morning. All paint came off nicely, but the surface has become softer. I'm sure I can still use them for this helmet, but I would like to harden them again so I can sand them and prepare them for the primer and paint. I definitely don't want these parts to let go of the primer, or be vulnerable to damage because of the softness. The primer will certainly be hard enough for the painting stage, but the surface of the resin might not bind or give way all together. What can I expose them to to re-cure the surface of the resin? The resin is a thick white plastic, unsure about the brand. The helmet came with separate ear parts and an rf rod with a metal pin inside.

I might try a few coats of finishing epoxy to give it hardness. that stuff dries hard enough to drill and tap it.

I recently bought some finishing epoxy from a hobby store, they use it to coat the balsa wood rc airplane parts. I just used it on my ear pieces that I made out of balsa wood. wanted something to protect the extremely soft wood from damage. after 2 coats and a few days, they dried to a hard plastic. I cannot scratch the wood underneath. hope this helps