What I have run into in an increasing supply is a huge number of variables that affect paint behavior, with many of them being difficult to impossible to control.
On top of that, there are many differing combinations of these variables that will give good results. Unfortunately, at leas for me, there is much larger number that tend to give poor results on almost everything I try.
A case in point the simple task of painting two half-hull pieces for Revell's HMS Victory. There is a copper bottom to deal with and then a rather simple black stripped yellow ochre hull.
Working at 1:146th scale (just about N-Scale) I found there were several little nooks for paint to run together that weren't obvious on the naked hull. The masking job I did to separate the copper painted bottom from the ochre was about as effective as using a piece of string. The masking smudges were multiplied by the attempt to provide the black stripes.
This is where Murphy's tongue-in-cheek principium comes into effect. I turned to my hobby store for a solution, which was pretty, much, start over. He suggested a household paint for removing the offending paint job and regular painters' blue masking tape as it was more aggressive. Oh yeah, scrap the spray paint cans.
After three-strike that-- (four days for good measure) of soaking in the cleaner I was dreaming of a clean return to the brown plastic. Nope.
The copper paint pretty much cleared from the bottom "plates" with the exception of the rudder and bow piece. Some of the yellow came off the hull, but anywhere there was detail (around the 100-plus cannon hatch covers for instance) the yellow clung and puddled.