I have not had good luck with brushes at all for MMU application. Expensive or cheap, natural or synthetic, washed with any number of cleaners and shampoos. My face, though I loved the look, became unbearably itchy. I tried using just a plain powder puff, buffing like crazy as you would with a brush. These are the powder puffs with a ribbon across the back. I put my two fingers through the ribbon and separate them, holding the puff taught. I also find I need to wait an hour after washing my face before putting on the MMU. Otherwise, the itching.
I hope this is helpful to someone!