'65 Commando valve cover cleaning

The valve covers on my original 273 Commando are basically in good shape, but are filthy inside with layers of gunk. The aluminum fins are in nice shape, and I understand that they are glued to the top of the cover. Normally I would have the machine shop hot tank the valve covers to clean them, but I think that the hot tank process would loosen the glue and damage the aluminum fins in the process. I have a media blast cabinet, but am not comfortable using it because I see no way of making sure all the blast media could be cleaned out. How have others cleaned these without damaging the fins? Is there a solvent that could be used that would not damage the aluminum or it's bond? My searches have not been fruitful, what have others done?