I don't know what your set-up is, but I have done many such applications, both in construction and repair of cockpit coamings. If your can remove most excess resin, try stretching electrical or PVC tape accross the coaming, over-lapping the tape by about half as you progress along.

A light sanding afterward will remove tape ridges. the only drawback is that you have to have a suface to stretch the tape to! (This works well on a coaming that is installed already).

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