A word of caution. I don't usually get involved with these things but, if the model has any clear coat remaining it will need to be removed first. The clear coat will likely act like a barrier and the only areas that will be chemically cleaned will be the areas with no clear coat. There are commercial cleaners/brighteners (Brite Dip is one) that will do exactly what you want but, unless you know someone in the industry, it's almost impossible to obtain. Good reason for that...very hazardous to the untrained and poorly equipped.
Jay
