Your brush is you most vauable tool and should become a part of you.
Brushes are made from sable .... sable is more expensive than MInk.
Would you wash you hair in acetone?
Why wash you brush in acetone?
I keep old monomer in a separate bottle and use this to soak my brush when needed.
But .... when you get better at ratio, your brush should never need to be cleaned.
Every 2 weeks (On a saturday) I shampoo my brush (with a good quality shampoo), if it's good enough for my hair then it's good enough for my brush, then I rinse, then apply conditioner, wait a few mins then rinse and pat dry. Give it a drink of monomer, then shape.
I go through about 2-3 brushes per year, doing about 40 clients a week.
If you use more brushes than this per year, you are doing something wrong.