Interior paint questions.

[jays88chevy]

I plan to paint my dash, door panels and other interior pieces of my 88 Chevy. Most of the pieces are made out of the hard plastic (dash, door panels etc.) and a few are made out of the hard padded vinyl (arm rest and center console). I want everything to be smooth looking with a high gloss. My questions are:

1. In order to get my dash smooth can I use a high build primer to fill in the the dash than sand it smooth or do I need to sand the dash smooth before adding the primer?
2. Will the high build primer work good on both the hard plastic pieces as well as the flexible surfaces on my arm rest?
3. Last, will a 3 or 5 gallon tank air compressor be big enough to paint these pieces? I have a 3 gallon one already but can barrow a friends 5 gallon one if needed. If I need anything bigger I will have to rent one.

Thanks
Jay