Out of all the "organic solvent based" putties, Testors Contour Putty has the mildest solvent package. That is what I would try first. If still too "hot" then I would go with Elmer's. Guaranteed that won't attack the thin styrene, but has a long drying time.

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When in doubt, WHACK the GAS and DITCH the brake !!!

Yes, there is such a thing as NORMAL, if you have to ask what is "NORMAL" , you probably aren't !
Failure may not be an OPTION, but it is ALWAYS a POSSIBILITY.
ALL systems are GO for MAYHEM, CHAOS, and HAVOC !