painting help
Phew...... Down the rabbit hole you go!
1. I am unfamiliar with nason, but I would guess close to a pint ready to spray for the engine bay. This is from me assuming you're going to do it white, looking at your color scheme. I know it may seem like a lot, but in my experience any "value line" is going to take more to achieve hiding. This of course will also be affected by the color of the primer or sealer you use. A white sealer or light grey primer will cover faster than something darker
2. This refers to the "thickness" of the base coat. 20-21 is time in seconds it takes to drain out of the standard measurement cup "zhan cup". Not something you need to worry about, mixing according to the ratio will ensure proper viscosity.
3. I would go with a 1.3/1.4, to ensure good atomization. Check around on the net for tips setting up whatever gun you use. Fwiw a guy who works for my company uses a gun he bought from northern tool every day on customer cars with great success. It is a roll of the dice, but sometimes the cheap stuff works good. It is important to let the paint dry between coats, that dull look is a good indicator of dryness, also you can touch paint you'll sand later like the tops of the fenders. Give it a good press with your thumb and twist, if it doesn't smudge or wipe off you're good to go. Should take 5-10 minutes depending on temp in the shop and reducer speed.
4. Don't try to put the clear on thick, this will lead to runs. To keep from having too much orange peel/texture, try to find the sweet spot for distance of the tip from the panel you're painting, usually 6 to 8 inches. But depends on air pressure, how fast you're moving, and the thickness of the clear.
As far as painting the whole car, the base coat will be fine during the time it takes to tape up the different color sections, even if it takes most of the day.
The best thing to do to make sure it turns out the way you want is practice. Even if it's on a coffe can or bowling pin or junk fender or whatever. Paint is expensive, but the shop I buy from usually has some mis-mixed base or old stock that they mark way down, maybe you could find something similar where you bought your paint.
A couple important things: you want the temp to be consistent as possible when you paint the car, and you'll need a lot of compressed air, if your compressor is struggling to keep up it'll be next to impossible to get the atomization you need for a good finish. Use a tack rag between coats of base and before your first coat of clear. Also invest in an air dryer, those toilet paper types are probably the best value, just make sure to change rolls a couple times during the job.
As always, this stuff is based on my personal experience and your results may vary. With the attention to detail you are showing and a little practice you should do just fine!