I fibre glassed my old boat that part of it was cheap but fibre glss isn't waterproof by its self you need a gell coat on top of it to make it water proof and I found that to be very expensive
The big trick with glass fiber is to roller the glass resin on the glass fibre and putting enough resin to cover the fibre cloth smooth, but not wet small pools of resin as this will crack.This will guarantee a good finish.