I'm planning to coat the underside of my Mark IV body this weekend and I've got some questions
that I was hoping you all could weigh in on.

What is the best way to prep the fiberglass?
Should I be using an undercoating product or a bed liner product?
Will the final result be a smooth or rough finish, and does it matter? (not sure if much or any of it will be visible in the engine compartment)
What brand(s) have worked well for you?
Brush on vs Spray on?
How many coats?
How much will I need?

Thanks in advance for your help.