That's one crazy machine. I saw that at the Rod & Custom show many. many years ago at the NY Coliseum. Those shows also had George Barris customs there too.
Besides all the wet sanding advice given the most important thing is to lay down the smoothest coat of paint possible and that will minimize your wet sanding and you'll start with the finer grits.
Box art:
Interior:
Body parts:
These will get paint detail work next.
The body, solid blue base coat w/blue metallic on top, I did the Molotow chrome last night, very carefully trimming the masking to get it right.