When searching the internet for some makeup video, I found a (supposed) expert site where a (supposed)makeup artist is shown making up a model.
Before each and every every step, the cute, extremely young looking artist says to make sure to blow on the brush after dipping it into blush, bronzer, powder, shadow, etc. HELLO - Where did you get your training? The school of how to spread germs - GROSS!
I am sorry, if I ever sat down to have my makeup done and the artist started blowing on her brushes, I would run the other way - and FAST!
If I have excess powder on a brush, I simply tap the brush over a tissue. And if I want to deposit more product down into the brush, (especially great for applying facial powder) I just take the brush, keep it vertical with the brush on the top end, and tap a few times. This will allow the powder to slip down deeper into the brush allowing for less waste and more coverage.
For goodness sake - DON"T BLOW ON YOUR MAKEUP BRUSHES! And be sure to wash them frequently.