[Enoch]

I have dipped several dozen cars all with no problemns. As for residue in the seams washing out with thinner and wire wheeling always take care of it. To get thinner into the seams simply fill up you paint gun and spray it in with high pressure then blow it out with a blow gun and repeat if necessary also wipe the thinner with rags before it dries (as you would with prep-sol) and this leaves it clean. I always da, wire wheel or sand the bare metal before applying a self-etch or epoxy primer.
As for trim tags ALWAYS REMOVE as the chemicals do eat the aluminum.