For what it is worth, I know from first hand experience that in the aerospace industry, the final "washing" of many parts that must be clean beyond comprehension (LOx-compatible clean!) is washed with orange Joy liquid dishwashing soap followed by lots of rinsing with water. Our tests showed that Joy, of all things, left the least film on both exotic aluminums and composites.
My usual procedure is to start with more agressive detergents, finishing with a Joy washing with a distilled rinse. Only then would I start prepping the surface for the next coating, such as scuff-sanding, etching, etc.
Don't forget to do more wipes between preps. You don't want to leave the residuals due to the sanding on your clean part before painting it. Solvent-wiping or tack-wiping is probably required.
Bill
