Old thread, but no harm there as the question is a good one.
Yes, I paint a lot with a brush. For the purposes of discussion, some areas of modeling invite more, or less, use of a brush. For instance, I believe the figure modelers almost uiniversally do their painting with brushes because the genre requires a lot of shade and shadow, simulation of the effect of light on the subject, and detail nuance.
I don't think armor modelers do nearly so much as their subjects tend to be a lot of one color. They'll use the ehand brush for details. I fact they often mostly assemble the model before painting it, and an airbrush really works best for that.
The llist continues, but you'll get the idea. I have deep respect for those who do hand brushing. If you look at model magazines from Great Britain, that seems to be a real art and is pretty commonplace.
Success also depends on the paint you choose. Since no one person has tried them all, read reviews on which paints folks think works best. It also changes constantly as new paint lines become available.
Get good brushes, it's very important. We all probably started modeling hand brushing with lousy brushes, and it turned off a lot of people.
I like to use a good flat brush for painting areas, say 1/8' to 1/4" wide.
Do not try to use the paint to cover up mistakes or as a filler. Work in thin coats.
And practice. It's like a lot of things, say cooking as well. The more you do it, the better you will be at it.