The process you are using is pretty much the correct one, though I usually pick BIN for priming when the wood is previously stained and varnished because it sticks the best. Spraying will help you get there in fewer coats for sure and the end result should be brush mark free, but spraying is generally not something a novice painter can just pick up and learn in a few hours. It takes a lot of practice and some good hand eye coordination. I prefer to use an airless because it's faster, but if you want to mess around with spraying, I would suggest trying to rent a HVLP unit because it's slower. Another thing you can try to speed things up is applying the paint with a little 4" roller and then brushing it out. This just saves you some time dipping your brush into the paint so much. The roller helps to get the paint on faster.

Properly applied conversion varnish does not flake. Neither paint nor conversion varnish nor any other coating will withstand abuse from too much water. MDF will always be far more stable with humidity swings than wood ever will.

1) In the communist state of California I can get Conversion Varnish from a dozen places within 5 miles of my shop. 2) spay outside only if the look you are going for includes bugs and debris. 3) A professional finish involves prep, primer and topcoat. Cheap usually results in cheap. (Automotive sprayer has skils but differet experience). 4) probably be better off going with what the finisher is comfortable with. Italian 2k is not hard just different and he won't like the fact that it cost more. 5)white is a pigmented finish not just red and yellow. White is actually more pigmented. Red would most likely use a clear base or you would get pink. 6) it's ok to call California a communist state we welcome it. There's way too many people here as it is. One fact to note in the 80's the smog was so bad there were days when your eyes and throat burned. If left unchecked today we would all be wearing gas mask like they do in China the other communist state.

I'm not sure, Nancy, as our cabinets are custom and went through conversion varnish process. Or well, some complicated process. Special booth etc. What I did find out though now when researching, that there are different varnishes, and not all of them are available in CA,due to very stringent CA rules: "A low formaldehyde version of conversion varnish is not available for sale in California because it does not meet the state’s volatile organic compound (VOC) standards. Keep in mind that formaldehyde is a VOC and once the finish of regular Conversion Varnish is fully cured before home delivery, there will be no VOC or formaldehyde breathable by the homeowner." found on the website of a CA-based designer-builder-there is a chapter on cabinets there that goes into expanations and details on different finishes, so it's an informative and interesting read. He does prefer conversion varnish to all the other paint finishes, (as also our cabinetmaker did) but is an opionated guy in how he writes ..)) Here: http://www.dndb.info/cabinets/ Would be great if pros in the field chimed in. I do suspect though that paints etc here lack certain ingredients..they remind me of my gluten-free food, like something is missing:) I wonder whether it's just my feeling. But then we don't know where the OP lives, so might not be relevant. There are several threads on Houzz as well that discuss subject, as far as I understood-I saw them when started googling-but I didn't get to reading them yet.