The difference in time that it takes to do a great paint job and a piss poor one is not much. Would be happy to coach you by text, starting with don't do any heavy work (welding or large dent removal) on a panel that's off the vehicle if possible.Front fenders and doors in particular. They tend not to fit back on very well after the fact. Sanding and light body filler work off the frame is fine, but only if you're not working on edges that need to match with other panels.
Wipe every thing you intend to paint with prepsol before you do any sanding. Keeps you from rubbing wax, or oils into the surface when sanding. Repeat before priming and painting and use a tack rag before every coat of primer of paint.
Bondo on bare metal is old school. The best way is to roughy the surface of the dent with 40 to 80 grit and prime it before you apply the filler. It's ok to leave some of the original paint on too as long as it's stuck on well. Bare metal under Bondo will eventually rust.
If your working on any plastic bumpers or clips make sure you use an adhesion enhancer like DuPont 223S or even Auto Zone
on any bare plastic before you apply anything else on it. There are also special primers for plastic that allow some flex.
Sand wet whenever possible. It'll save you a bundle on paper and time. The only side effect is that your hands will dry out and crack after awhile. Use the wife's hand lotion at the end of each day. Start with 220 or 280 and don't go down to bare metal if possible. Your primer will bond better to the old paint than it will to bare metal in most cases. Finish with 400 grit before priming and use a two part epoxy filler primer. The stuff is amazing and will fill a lot of scratches and seals Bondo well. Wet sand it with 600 and then 800 before painting. The rougher the grit the better it sticks mentality is old school as well. 800 overs more scratches per square inch therefore it holds the paint better and you won't be able to see the scratches up close like you can with a 400 grit finish.
Use a base coat/ clear coat for the final finish. You can get away with murder using base/clear. Almost Anything you do wrong can be turned into perfection with a bit of sanding and polishing. I'll post up a couple of before and after repairs I had to do on my bike recently.
Paint the door jambs, trunk, under side of hood, etc separately and then bolt your doors, fenders and lids on before painting the car in one piece. You can run masking tape around the edges of the painted surfaces befor you spray the car and then remove the tape befor you clear it. By doing this you will be able to later buff the transition and make it look like you painted every panel off the car which is a terrible idea unless you have a dozen skilled buddies to help you put them back on after painting.