the way i do it is to brush on a good layer of gelcoat then start to put the fibreglass and resing in, u just gotta watch out for airbubbles in between the gel coat and resin.
if u cant get gel coat then perhaps u could just brush the resin in with a couple of layers then fibreglass it. probably be what i would do but im not that nolagable as some members of the lair.
You've done a great job, very well done.
When using plaster i use scrimm or hessian to reinforce the plaster, less breakage that way, you can use a polyurathane resin instead of a gel coat, i use this method when i mix filler powders into the top coat, like alluminium or brass, works better than gelcoat, you can also mix some ordinary filler powder into the alli resin to thicken it
Anyhow, can't wait to see the finished bio's