I'm doing most of the work myself on my '31 Coach (some call it therapy!) and soon need to prime and paint nearly everything. Bought a 2 Cyl model 34 Webster Compressor mounted to 11 gallon tank at Auction on weekend for $40, got it home and air tank is toast(pin holes etc likely from water left in tank). Compressor and Electric motor and belt drive is great. Can buy new 20 gallon tank with mounting plate and fittings for about $300. My question is will this likely provide enough constant PSI/CFM pressure to operate a spray gun and enable a decent DYI paint job? I don't mind if I have to paint one major item at a time as I have limited space anyway.

I guess you don't have a clue as to the output of the motor compressor combo in CFM@ 120 PSI? or the HP of the motor. is the motor a 120 volt or 220 volt motor. I use a 6.5 Hp 220 volt with a 60 gallon tank and have the shutoff set at 130 psi. it puts out around 16cfm @ 130PSI. It keeps up with a spray gun, but with a pressure sandblaster it will drop down below 100 psi after about 5 min of sandblasting with a average sized nozzle, I have to wait about two minutes for it to get back to 130 psi. but lately I haved connected my 3hp portable Black Max compressor with a 20 gallon tank up and with both compressors running I can keep blasting till the 40 gallon sand tank is empty.

You can paint with a 32 (how Novel) gallon Tank but for a blaster...go big. Expensive...can be...pay for it's self? Definitly.

It depends on what you are spraying with. You should use a good HVLP. Although it uses more volume, pressure should only be about 30lb so you could manage with an output of 11/12cfm at a bare minimum. You need to look up and find out what the specs.are on that pump and motor first.

That's at the gun.

The basics to obtaining a good/great paint job on your car begin with the preperation. Remember, you can't shine S*#T! Take the time to sand, fill, and whatever else it takes to make the sheetmetal ready for refinishing. Be Patient!
Clean Dry Air Supply is a must. A rusty old air tank of any size is unacceptable. Pro shops have air driers in the supply lines. All we can do is use a moisture seperator in the supply line and add a final filter at the connection to the spray gun.
Mix your materials accurately. I save used glass jars and mix materials in them. You can place your own measurement marks on the outside with a Magic Marker and re-use the Jar to obtain a recurring viscosity or even adjust it.
Applying materials can be challenging to any novice. Tha KEY is to take your time and have good lighting so you can see what your applying and where it is going. Add extra time between the very first coat and the next. The solvents need more time to disperse on the first coat as the surface is harder to penetrate than fresh coat over fresh coat.
Unless your doing a restoration the Base Coat/Clear Coats will give your work that "Pop" that we all strive for. Don't hessitate to PM if need arises. Good Luck, Al W.

One inexpensive alternative to a Desiccant dryer is what I use on my comp., an "old" (if you can still find one) universal after market A/C condenser and an electric fan. This has slip-fit hose connections and can be placed between the pump and the water trap to the tank. If you find one that has been used as an A/C condenser then you will need to flush it clean of any oil first. When hot air cools it condensates in the trap and I have had pretty good results from my set up.

Professional shops use dryers that cool air with an A/C- Desiccant unit and even with this if the volume of use is high on a hot day you will still get some moisture in the lines.

Thanks for advice guys. Found a great site on Google that explains all the do's and don'ts of spray painting from prep, equipment, techniques, filling, etc etc to polishing. The comp I bought has a 1HP electric motor and 10 gal old tank. Appears a 60 LB tank and more power would be required. Have a veteran body man/painter who is trying to retire from the business who may be able to be enticed into painting it for me as he loves the older cars (he has a gorgeous '40 Chevy coupe with all the accessories and is a VCCA member). Current thinking is to leave such a critical job to the professional.

Is water-borne paint feasible for DIY painters? Is moisture in compressed air a concern with waterborne?

While it covers better it requires spacial drying procedures and takes a good bit longer to use and dry. At work, only the base coat is water-born. We still use urethane primer and solvent based clear.