The brand of paint you want to seek out is Createx. That was one of the first tips I stumbled upon when I joined pinside in 2014 and man, that stuff changed my life approach to detail painting. It mixes and blends consistently, and flows like an ink dream, cleans and corrects easily, and sets with heat. Pricier than cheapo craft but awesome stuff that's worth the expense; the primary color set is pretty close to the "stock" colors used on a lot of playfields: black, white, and red are especially near dead-on in my experience.

That said, I'm not above using craft colors when a match is convenient. The problem with them as you have discovered is they do not thin well. And don't even waste your time trying to thin light colors like yellow: thin enough to flow makes it pretty much transparent and useless; you have to add so many coats that way that you're pretty much back to "bottle thickness" in the end. So thin as much as makes you comfortable, but realize there is only so much you can get away with, and learn to adjust to those limitations.

In all cases, use the best quality brushes you can afford. I mean the individual $5 "000" and $5 "0000" brushes for detail work, not the crappy "thin brush" from the assorted 10-pack for $5. A quality brush holds more paint between reloads, dispenses it evenly, and most importantly holds its shape. And they can be cleaned and reused a lot more, too.

As for the paint loss issue: if it's only with tape and adhesive, then short of maybe using post-it-notes, there's not much else you can do. Still, I would be very worried about (near) long-term adhesion issues with the paint if frisket is pulling it up. That pf might be a victim of who-knows-what, and it might not be long before ball pressure and incidental wear starts doing the same. Before you invest too much time and effort into your paint work, I would be very aggressive with test burnishing and rubbing on the playfiled just to make sure that old paint is going to stay stuck. You don't want it to start flaking on you after hard work. You may not think "normal play" is that bad but things happen, if not during play then during shop jobs and the like.

The airbrush is your friend but requires lots of patience and practice. Light colors will be your nemesis and may take many thin light coats to look right. Darker colors take longer to set up and teardown the brush than it does to get coverage. But know that an airbrush will absolutely put paint in *any* nearby air gap. Meaning if you don't have solidly burnished airtight mask, you better not airbrush.

One advantage to cleacoating after paint is, a nice clear job can make subtle brush strokes disappear

One final thing: with acrylic paints, don't be afraid to make minor mistakes. Even in a bad case, most of the time you wipe off or scratch off or sand off, and recover. Just approach it carefully and remember every step forward is another improvement.