I made a mold to make a radio box, I am going to layup fiber glass in the mold. I am going to use
modeling clay to round out the inside corner of the mold. I tryed to wet my finger to smoot out the
clay, it did not work that well. Can any one tell me what would work good for this that I can glass
over? Thank you for any help.

Good question. I would try the Tips and Tricks section in the Airplane Forum.

I would try and form the clay again but I wouldnt directly use resin over it. You should paint the whole mold inside with PVA glue which the resin doesnt stick to. Thats common on making molds.

Bondo has always worked for me. Just make sure to seal it off and use PVA release as previously suggested.