First, I wet the brushes and take a bit of liquid dishwashing soap and apply it to the wet brush. I gently massage the brush and then rinse out under warm water. I apply a tiny bit of hair conditioner to the brush and then take the brush and soak in plain warm water for a few minutes gently pumping it up and down to get our more of the dishwashing soap. I then soak the brushes in a solution I of about an ounce of white vinegar, a squirt of glycerin, and warm water again gently pumping the brush up and down in the solution. Another rinse, shake, gently rub the brush around a soft towel and let dry.
I read about this method about five years ago and have been doing ever since. In fact, when I get a new brush I do the same thing and it removes the smell, if any, on the brush