So I am working at my uncles fiberglass factory now and getting more hands on experience. We seem to go back and forth on how things should be done and how they shouldnt. I dont know his level of actual knowledge but he has worked with fiberglass for almost 30 yrs. We have a plug that we are wanting to rework to make new molds for a customer of ours. It just has a few waves and dips here and there. I said I could do body work and have them done in no time. (I have a degree in autobody work) I then said that it would be sprayed with an epoxy or urethane primer, wet sanded and buffed and call it good. Hes saying that it cant be done this way. Whos correct? I have thought I have often heard of people doing this with no problems. Hes wanting to try and sand just the high spots with 1200 grit and call it good on the plug. I said this would be to fine of paper to get the waves out and that it would just create more problems just sanding one spot only. He hired me for my knowledge in both composites and painting, but never listens to my advice on anything and its starting to annoy me. 

Depending a little bit on what the plug is made from, I would say that You're right ... Do it properly ... 1200 grit will not remove very much material, so will probably not remove all the "wavyness" or uneven spots.
Skimping on the plug makes for more work on the mould, and/or more work on the finished product ...

Knowing what the plug is for, and what it is made from will give you better feedback from this forum ... 

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