> Painting is constant problem solving.

Turn off your brain and paint away. Doesn't have to be a Rembrandt but something interesting may come out and most important you enter flow state. I'm a prolific painter and there's a bit of problem solving involved but that usually solves itself by working on other pieces and solutions ensue by themselves when you return to problematic works. Always works out for me. I never work on one piece at a time but 10 or 20 without any outside pressure. The more you do spend time 'doing' the better you get without being frustrated/stuck thinking about it. Good luck

The problem with flow state is that there's no growth in it. It can be productive if you're already very good, but learning a skill, esp. learning something very hard like realistic painting, means years of problem-solving, overcoming obstacles and straight up banging head against a wall ("what I'm painting does not look the way I want it to look, and I'm out of ideas on how to make it better").

What I would do: Dry learn a few new techniques then shut off the brain. Fun practice in flow state then revise a few sessions later. You may have misused some of the techniques but nailed a few and may as well have come with an original hybrid. It is imperative to have fun and dial down on pressure otherwise it gives rise to frustration which is valuable in itself when self critiquing but it is also an enemy to productivity. I apply the same philosophy with learning instruments and it works quite well. Is it slower than other approaches? Maybe, but my goals are to first have fun then to get better. Also it is a productive disconnect from programming and work. But also keep in mind that this works for me and may not work for you. But in order to find out you have to give it a try. Good luck:)