Now that I think about it I remember you bought Poly resin.
If so that is surfacing wax. For future reference, buy laminating Poly for initial layup and finishing or "waxed" Poly for the final coat. You can actually buy all laminating resin and the wax additive for it. The laminating resin stays sticky so there is minimal prep between coats. You use the finishing resin for the last coat as it has wax that rises to the surface for a hard finish. I know this info may not help if you are just hot coating some pieces but it will definitely come in handy for things like your transom etc..
I would wash the piece down with a water/acetone mix followed by a light sand, repeat as necessary.