To be honest I think your going about it the hard way , as it will take alot of sanding and re bogging (thats what we call filling with epoxy) to get it to the point your happy with it ,
I used to build my helmets up by cutting up 4 and 10 litre plastic paint pots and hot glueing them together and using a cut up helmets (bike ,batting , hard hat, even a horse ridding helmet once) for the domes, then the only thing needed to be bogged up were the seem lines , then once I got to a point were I was happy with them Id make sillicon molds , then pull fiber glass casts, then Id cut up and rework the casts and remold
Any way, its a learning experiance , just keep at it and take on what people tell you and use what works for you , and in the end its sadisfying finishing a helmet that you built up from the ground,