White stuff leaking from under voltage regulator?

Acetone will dissolve that goo, but don't use it unless you're willing to lose a lot of paint too.

I scraped up some of the goo with a painter's 10-in-1 tool and tried soaking blobs of it in different liquids. Vinegar did nothing. Diet Coke did nothing. Acetone completely dissolved it in a few minutes.

Lay a paper towel on the goo, soak it in acetone, and cover it with cling wrap to keep the acetone from evaporating too fast. Then lay a rag on top to keep it all pressed down. Come back a few minutes later and rub off the softened goo (and paint) with the acetone-soaked paper towel. Use a popsicle stick to scrape harder if needed. Repeat as necessary. Repaint if desired.