Hi, i used a cross woven fiberglass its the best way to get into small grooves. Take epoxy resin
its the better way as the polyester resin. Take a mean size of fiberglass under 1mm. Make even 2
or more layers depends on how thick you would have your pieces.
Use only the epoxy resin on the outside first to harden your pieces. Be careful. Make a form for the
inside because the pieces would be soften the first time you use the epoxy resin and they will be deform
if you have no form to hold the appearance.
Hope this helps a little bit.
Good luck. Would be interesting to see your next steps.