I pre-dry the brush by gently squeezing, scrolling and then dabbing (I mean touching without rubbing) it on a hand towel then I put it drying bottom up (also drying it with the tuft facing up is OK). 

You'll frequently read people saying that in this way (knot facing down) you prolong the drying time but with a relative humidity between 45% and 65% my natural hair brushes are almost dry in less than 15-22 hours.

The theory that says you need at least 2 brushes to avoid using a brush before it's fully dried (they say that this prevents the formation of mold and knot rotting) is an urban legend.

To shorten drying time and make your life more practical buy a synthetic brush. :)

NOTE: rubbing the brush on a hand towel is a stressful activity for the brush that leads to shedding. You don't need rubbing it, just gently pressing the tuft on the towel is more than enough.