You wont need to do all that with clear shells, as the work would be done on the inside...Spray with plastic primer.
Sand with about 300grit.
Spray with plastic primer.
Sand with about 600grit.
Spray main coat.
Sand with about 600grit.
Spray main coat.
Sand with about 800grit.
Continue getting higher until you're happy with roughness.
Spray with clear lacquer for shiny effect. Leave for Matt effect.