You shouldn't ever be painting from out of the bottle. Brush painting is most successful when you use thinner twice.
You move some paint into a palette depression (or cup), closing the paint jar right away. You load two depressions in the palette with thinner. One is to thin the paint with, by pulling thinner into the paint depression and stirring. The other is to load the brush with thinner. (many people use only one thinner depression, also).
To paint, you dip the brush sideways into your thinner, patting some of it back off on the edge, then you dip the brush into the thinned paint. Whenever your brush "seems dry" to you after you stroke paint out of it, you reload the brush with thinner again, then go on painting.
Many people just dip their brush into the open paint jar, painting away while they leave the cover laying on the bench. Then they clean very aggressively to get all the paint out of the brush. They also have problems with paint life. (the partially dried paint builds up on the jar sides and in the lid every time they use that color) A pre-loaded brush is also easier to clean, because you don't get dried paint in it in the first place.
I learned this in a Jr High art class,,,,,,I was "already a good brush painter" when I walked in on the first day (in my own mind), with many years under my belt (6 years or so). When the art teacher saw what I was doing, she actually slapped my hand with the brush in it. Then she taught me how to use a paintbrush and how to clean them using hair conditioner for longer life.