cant comment on the vpa that chris recommended since i have never used it but what i can highly recommend is adtech p14 or p17 filler. works like a regular filler but its a solid structural plastic when cured so its hard and has strength. wont soak up solvents or shrink. its highly heat resistant as well. in the marine world, its really popular. def ditch the regular filler. the glaze you have is fine for filling pinholes, etc. after a wash your going to want to wipe that gel down with acetone or urethane reducer. god only know what type of release they used on their molds. could be wax, frecoat, pva. you just never know.