Coming back again--had some questions

Hey all. It's been almost two years since I last modeled a car. I left it because I coudln't contribute any more time to it since college is pretty demanding. I want to come back again because I was cleaning my room up when I found my unfinished Toyota Supra, Lambo Countach, and still in box Revell Enzo, and Tamiya Skyline kits.
I studied through the FAQ for beginners, but still had some questions that are buzzing in my head.

1) Do you guys paint the parts (engine blocks, exhaust pipes) BEFORE putting them together or AFTER? From what I've seen, I think its usually done before.

2) Please tell me if I have the steps for painting the bodies down correctly, as it has been a long time since I last did it:
1) Sand, and clean the body
2) Prime it at an arms length away
3) Prime again, except closer
4) Let harden for 24 hours and sand and clean where needed
5) Clean with warm sopay water and paint with color
6) Follow steps of painting, given by P-man
7) Allow to cure for at least 4 days
8) Sand using 1200+ papers sequentially. This will cause the whole body to become dull and scratched
9) Polish

and my last question:
3) I have Krylon all-purpose spray paint and some automotive paint and automotive polish. Are those okay to use? Or will I have to go and purchase modeling-specific paints?

Thanks!

Welcome back to the hobby. You've asked alot to cover so I'll just suggest that you've got the basics down, but check out the WIP's on this forum for answers to your questions.

There are a great many ways of completing a model. Ultimately you will have to choose the best way for you based on your skill set, available tools, and time.

Automotive grade paints are a great way to finish your model, but stay away from the Krylon all-purpose spray unless you know the primer underneath will definitely protect the plastic. This brand of Krylon is very strong, but I've used their yellow on the Revell 2006 Z06 Corvette without a problem.

Hey, thanks a lot for your feedback!