I have done this as well,,not being to familiar with Mustang trim is that metal or rubber?
either way I usually use a wax and grease remover,window,or rubbing alcohol dilluted with water
if it is damaged rubber trim sometimes you can use lacquer thinner on a white cotton rag and pull it across the section in 1 direction,not back and forth but I would only try this as a last resort .
I usually followup with a water based dressing
EDIT,,I have been goofing around with Rain X waterless wash on different things and found it handy for removing wax and compound splatter and residue of off of rubber and plastic surface,so if you have any waterless wash give that a try