I am not sure why a person would want to add a layer of material to an existing functional paint job.... Why the desire to have it "show car shiny"??
Please, this is not meant as a disparaging remark, just do not understand why the original finish is not enough? I have had a similar discussion on classic car boards where folks spend crazy amounts of money to give their car a "10 feet deep" shine.... The trend in that world is actually finally going back to more original finishes winning shows instead of the super glossy paint jobs.