I get where you are coming from. Some of your challenges are easily fixed, especially the paint drying too quickly:
Make yourself a wet palette - it sounds like you are not using one - it is honestly super easy to do, there are plenty of youTube videos on this topic as well.
This Mega Brute was the first model I painted. I did once paint a dwarf model about 10-12 years ago or so but nothing since. I regret painting the "Boss" of my Brutes first. You can clearly see how untidy I am, paint splashes on the yellow armor, yellow paint on the face... it was messy.
I do feel like I am making Progress though, these are the rest of the Brutes and overall I am much happier with them than I am with their "Boss".
I doubt I will ever get as good as a lot of people on here are (there are some really damn good painters on here) but I think I will get good enough to not be embarrassed by the models anymore haha.