It's been about 20 years since I've done any serious painting but my process went something like this...
- Remove all moldings and trim
- Strip old finish to bare metal
- Perform necessary body repairs
- Chemically treat metal surfaces
- Apply maximum corrosion resistance primer, i.e., epoxy, self-etching, etc.
- Apply primer surfacer
- Block sand (and I use that term loosely... whatever tool is necessary to achieve a perfect surface and it's not always a block)
- Repeat the primer surfacer and block sanding steps (typically at least three cycles) (different shades of primer can be used to help highlight imperfections)
- Apply Sealer
- Apply the color coats
- Sand between coats when appropriate (this is dictated by the type of finish being applied) (do not sand the final color coat especially if it's a metallic color)
- Apply the clear coats
- Like the color coats, sand between when appropriate
- Allow the paint to fully harden (typically 60 days minimum)
- Sand and polish to perfection
Note that all finish sanding, whether body repairs, primer surfacer, color or clear coats are done by hand as that is the most accurate method. In fact when I read about colorsanding/wetsanding with a DA it makes me cringe. Although with today's grits, i.e., 3000, 5000, etc. machine sanding might be feasible, hand sanding is still the most accurate method to the perfect panel in my opinion.
This is just a quick synopsis off the top of my head... It's been a while. There are many more steps sometimes performed. An example could be completely disassembling the vehicle after the body fit has been established to paint the car in pieces. That is the best way to ensure the jambs are as perfect as the exterior and to minimize any unwanted overspray where it shouldn't be and also to eliminate any paint build-up in panel-to-panel seams.
I never did any $30,000 paint jobs... but I did do $10,000 jobs back in the 1970's through 1990's. The man-hours involved where in the hundreds... 200-300 hours or more were not uncommon.