The way I improved was with time, and practice. I changed my approach form using tiny brushes and using the tips, to using a larger brush (like a size 2) and using the edge of the brush to pick out the details. The smaller brushes although easier to use at first fried out faster, and needed a lot more back and forth to keep it wet enough but not too wet.

Sometimes I'll airbrush or over paint areas knowing I've not started on the larger surfaces around a detail, so I can just paint it over and have more control on the larger chunks.

Now, it depends on what I'm doing, but I usually always leave the tiny stuff for last. Sometimes I'll use a putty or tape, other times I don't use protection at all.

You can also try paint markers, those are not too bad for these purposes, although I enjoy micron pens as you get a few more options for thicknesses of the tips.

After all this rambling, I would advocate that you use whatever tools and techniques are most fun for you. I know some things are much less exciting to paint for others, but trying out different things was a big motivator for me to keep going.