An adhesion promotor is available from 3M with ref. 5917.
Automotive paint manufacturers also sell them.
However loop says that polyester doesn't need a primer.
Anyway, here's something quite interesting that I found out (even if a bit out of this league) :
I do think that a primer although sometimes not an uncontournable need, does provide a better adhesion than using paint directly. This in most cases, but I cannot give a good opinion about polyester.
Read about it on my Blog
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