Fabricating trunk mold

I have always done 5 layers if it's chop, 3 layers if it's weave

I think I am just going to begin adding some fiberglass reinforced body filler over the 2 layers of resin that I have applied. One thin layer of the filler should give it the same amount of strength that the 3 layers of resin would have given it.

Ok I'll tell you a cool short cut that I learned.  Do about 2-3 layers chopped fiberglass then get some dura-glass and fiberglass resen and mix them to gather to make a soup then add your MEKP (hardeners) and pour it into the fiberglass then swish it around untill it coats the whole thing.  do this a couple times or untill desired volume is acheved.  This is what I did for mi 12" sub enclosure which I mounted inside the spare tire.  Thats right inside the spare tire.  The box fits into my spare tire rim so that I still have a spare tire.  I used Masking tape and wax to fiberglass to. (credit for this goes to the whole Nov-Dec Ritop Class thanks guys.)

Today I pulled out the beginning of what will become my trunk mold. I am now going to begin using some body filler on the pieces to smoothen them out. Are there any products that you would recommend?