ok what i would do is after you pep they helmet you would have to put fiberglass resin (same thing as resin) then let it dry for about 15-20 minutes but don't do the whole helmet at one time so start at the top of the helmet and work your way down to the bottom, after you do that you can if you want to but another layer or just keep it the way it is but another layer will make it just a little bit thicker, after this step you are going to want to either put rondo (bondo and resin mixed) on the inside of the helnet or use fiberglass resin and the fiberglass cloth, recommend bondo faster and easier, after this you have to put to put bondo on the outside to harden it even more, after you sand it down till it is very smooth, you are also going to want to resin the visor and bondo the visor, after this step you can cut of the visor with a dremel