When the soap gets too contaminated by the paint, rinse both your hand and the brush with water, then get more soap and begin scrubbing again. Do not use lacquer thinner, shellac remover or acetone to clean brushes. Avoid letting paint dry in a brush. This will cause the brush to lose its shape, brush hairs will fan out, and eventually, the brush will be unable to be used.
When you use dish soap to get the sticky oil paint particles off from the bristles and perhaps the ferrule as well (we talk about this later), the oil paint comes off very easily due to the lowered tension between oil paints and the water. The paint will dry in the heel of the brush near the ferrule, making it difficult to be removed.
Scrub the brush back and forth across your palm, letting the soap penetrate the bristles to pull out more oil pigment. You can use turpentine (or Turpeniod - less smelly) to clean the paint out of the brush hairs, but also use it as a thinner for the oil paints.