OR !
Create your templates so that there are no hidden faces
this is difficult as it requires you to modularize very carefully from a finished template, I used google sketchup for this.
like this for 1920's style cars (sedan - 5 models / sport car - 1 model / truck - 1 model with 3 different cargos):
- base 1 model
- motor 4 models
-cabin 3 models
-trunk 2 models
-wheel 2 models
-stering 1 model
-hood 4 models
-bench 1 model
-doors 2 models
- floor 1 model
-barrel 1 model
boxes 2 models