I plan on painting my car and following these steps what do you think. Its going to be single stage wimblton white.
1. sand with 150 but not to bare metal.
2. body work.
3. prime body work.
4. sand full car with 220.
5. seal. (Primer-Sealer DuPont 2K UltraProductive)
6.paint. (dupont)

 

Wouldn't 220 be a little rough. I just did mine with 400.

 

400 or 600 would be a good choice.

 

After sanding original paint (if it is in good condition) the new school of thought is to seal everything with epoxy primer and then do your fillers and sanding primer on top of that. Epoxy is very tough and will stop rust dead in its tracks and gives a solid foundation for painting..
Go to http://www.hotrodders.com/forum/body-exterior/ and read up on what you want to do. It is a forum with pro painters who are pretty cool to newbies and willing to give advice. Also check out SPI epoxy primer, primers and clearcoats for excellent products at a very reasonable price.
Our site has pictures and info on how we painted The 66 if your interested