I assume you mean latex paint.
First: when painting the bristles should not be dipped in the paint more than halfway. This will keep the paint from over accumulating on the brush and will help avoid dripping.
It is important to rinse the brushes thoroughly after use. Keep rinsing until the water runs completely clear. It takes a long time but it's worth it. Once it gets to a point where the water is only slightly cloudy I usually fill a bowl with water and press the brush from side to side against the bottom until the water gets almost opaque, dump the bowl and refill repeating until all paint has lef the brush. If you use the brushes for an extended period you may want to change brushes and soak the used ones to avoid having the paint dry around the upper bristles and ferrule (the metal part). Then when the job is done, wash all the brushes at once. If the paint is already dried you can remove enough of it to make the brush usable again by combing the paint out with a painters comb or brush. You can usually buy them at any store that sells paint supplies. Soak the brush in warm water for about 10 minutes or so, then run the comb through the bristles from the ferrule to the ends until they are pliable and mostly paint free, rinsing often. You will have some speckles left on the bristles, but the brush will be usable.
