I am building an ODST Helmet and I don't know how I am going to work with the inside and outside once I have resined the outside and used that 2-part plastic 300 stuff on the inside. I know that many layers are needed, and that sanding is needed for the outside (possibly some bondo) but I don't know what to do about the inside other than adding extra plastic layers. Is it just a resin/ paint n prime job, or is thier another step Im missing?