James, I appreciate your sensitivity to the stuff; acetone is actually probably too strong for the fine details of the radiator fins anyway. The dishwashing detergent method does work -- I recommend dawn if you can get that in CA. Simple Green is another product that works. Just be careful when giving the parts the scrub-a-dub -- this material is a bit more brittle than polystyrene (not impossibly so I would add).
Thanks as always for the support, James. Please don't hesitate to ask any questions and if you have any problems, please let me know!
Cheers,
--Bo