I agree ---- far better to have too much than too little. With modern coatings that "cross-link" with each other chemically as they dry, you've got some very definite time windows you have to "hit". Once you've laid a coat of something on, you have to wait at least X amount of time (usually from 15 to 30 minutes) before you spray the next layer, but no more than Y amount of time (usually a few hours - RARELY longer than 24 hours). It you wait "too long" then you have to go back, sand the previous layer to rough it up, then lay on another coat of the same material before you can resume, otherwise you risk having problems with adhesion between layers later on. (Think chunks of paint falling off the car.) That's why you for sure don't want to run out of something in the middle of a job. Before I start on the "real" paint job on my car I'm going to have 7 quarts of base (10.5 quarts sprayable after I reduce and activate it) and 6 quarts of clear (12 quarts sprayable after activation) on hand. I'm planning on 2 medium wet coats of base, 4 full wet coats of clear.
I'm in the process of my first ever paint job right now. I shot the jambs, backs of the trunk and hood, cowl, etc. last weekend and _almost_ had a problem. I started with a quart of base and it was only enough to get one coat on. Luckily I was shooting late Sunday night and was able to get by after work Monday to buy more base to lay on the second coat before the window ran out. The tech sheets for the base I'm using (PPG DBC 9700) recommend no more than 2 medium wet coats.
That's another thing. Be very careful about who you rely on for information. Different manufacturers have different recommendations for their products and that's what you should listen to - after all they make the stuff. Even the counter guys at whereever you buy it will sometimes not bother to keep up to date on correct procedures, so always cross-check what they tell you with the tech sheets, and don't be afraid to call the manufacturer's product tech lines - after all part of the price you pay for the product goes to support those.
Let me recommend some educational materials and another forum to you before you get started. The materials are Kevin' Tetz's "Paintucation" DVD's. You can get them from lots of different places, including his web site.
The forum is his forum: Kevin Tetz's Paintucation Forum
. Kevin is there often and there are other regulars on there too who are at least as honest and helpful as the folks on here are. They've sure helped me. I may be somewhat experienced at the mechanical end of building cars, but I'm a definite first-timer when it comes to anything paint and body related. I couldn't have gotten to where I am on my car without the DVD's and the folks on Kevin's forum, and that's a fact.
On my car I'm using everything I can from Southern Polyurethanes
. Their products are very good and the folks there definitely know their stuff and are willing to help. The only reason I'm not using their base color instead of PPG's, is they don't make any. Their epoxy primer, which I used both as a bare metal primer before I started body work and also as a sealer (reduced 50%) sprays out very nicely and is extremely tough. Straight lacquer thinner barely softens it once it's cured. Their Universal Clear with their 'very slow' activator I put over the base --- my gosh, the stuff laid out like glass. There are places on the back of the hood and trunk that I don't see how it would be possible to get them any flatter or shinier even if I wet-sanded and buffed them. I can't wait to see how the "real" paint job turns out after I cut and buff it...