Ever try a 4-inch angled brush? @dakota194, that's what finally got me to stop fighting my trim. It holds more paint so you're not dipping as much, which cuts down on those messy lines.
Oh man, they were totally right! I used a smaller brush for years because I thought it gave more control. Switched to a 4-inch for my last project and it was a game changer. You cover so much more area way faster, and it still gets into corners just fine. My trim work looks smoother now too, with way less streak marks. I wish I had listened to that advice about ten rooms ago.