What you will see next is what I use to build up the mold. It is called pattern dough.
It has 2 parts 1 part is yellow ,and the other in blue.When mixed together it will make it a light green. I use a mixer for this job Thanks to Christy i have this for X mas. I use a board to roll it out to get it about 1/2" thick. Then use a glove and some alcohol to smooth it out. Then 1 layer of 6oz fiberglass to lock it all together. and let dry over nite.