Hello,making a plug for a motorbike tank from the original tank.
I have sanded it down and used filler primer as there were a few
small dents and scratches,they have all been filled and smoothed,
next I will polish the top half.I have got mould release wax,
semi-permanent release agent and P.V.A.release agent.Which off
these would work best on the filler primer.

   Cheers Paul

Anytime I have a plug/pattern made of different compositions (wood, primer, unknown plastics, etc) I just use PVA to be safe. I spray it on and it leaves an amazing finish. Eliminates risk with no set back (in my experience at least).