And Thank you "dirtyfingers", The formula number I gave you for an orange mid coat is pretty much universal for orange mid coat in PPG and would work in your situation...You are correct and I've said it before on this site, "life is the easiest thing we go through, only people get in the way". To many people don't care enough to listen, learn and just give rat's you what to go just a little up and above what's required of them. That's the difference between a caring jobber and one that just wants your cash.
Price is not always an indicator of quality, but, if you compare PPG's Deltron to Omni, there is a big difference in price and quality. I've had discussions with several paint manufacturer's management people regarding cost of there "higher quality" paint and have been told that people are paying for advertising (Jeff Gordon and Dupont), expensive gifts to major body shops under contract (I know several in my area) and warrenty. So is automotive paint over priced by major and the big manufacturer? The simple answer is yes, but they also do have quality products today in comparison to a few years ago.
What kind of primer and gun are you using? Generally a 1.8 tip is plenty big enough for automotive primer and I prefer a smaller tip for better atomization which results in a more even and flatter finish. Please excuse me for saying this but 1.8 tip is just a bit of a garden hose and your more pouring the product on as apposed to spraying it on.
Don't know if I'd spray a gun or two of the base coat your putting on your car to get it right, your call and I appreciate you wanting to get it right, but that's lots of money for learning. If you buy your paint at the PPG jobber, tell him to throw in a quart of mis-matched base coat...should be free for what your spending and practice with that.
Hope this answers your questions for now, if you need any more information I will try and help.
Best to You