I've built a bunch of stuff with composites. For large objects that will retain the foam inside, the moldless construction is a very practical option. Conversely, for hollow objects of any manageable size, I have found that it is best to go the extra step to make a mold. The finished part comes out so much better. You can also make duplicates.

In your situation you would coat the plugs you have made with a couple of thin layers of epoxy and cloth. You then finish the surface to look like the final part. (I like to put a coat of automotive clear coat on last.) If needed, make some sort of parting line (flange) with Formica sheet. Wax it up. Spray on some PVA.

http://www.fibreglast.com/showproducts-category-Mold+Releases-23.html

Next, spray on (or roll on) gel coat. Then build the mold using chop and  polyester resin. Pop off the mold with compressed air.