Bought a can of aircraft paint stripper based on some forum recommendations, since the acetone didn't work. In a twist shocking to no one, the moral of this $25 can from Advanced Auto Parts is to buy all your automotive fluids from Walmart or, better yet, Rural King.
https://www.thesamba.com/vw/forum/viewtopic.php?t=608000Within minutes, the paint boiled up enough to slide right off the "curiously filed down" location where the stock VW engine case part numbers go... This was followed by a spray down with brake cleaner, followed by a hot water rinse, followed by a blow dry from a shop vac, and finally a wipe down with mineral spirits to seal the surface again.
I just did a small patch for testing. For the rest of the engine, I will definitely be going *outside* to ensure adequate ventilation and safety from overspray.