Judge brush for better or worse, the most critical is the texture of the brush.
Synthetic hair is hard to the touch, easy to brush color. But it is durable and easy to clean. But some brushes requires a certain hardness to achieve better looking results, from natural and synthetic hair to mix and match.
Bristles to structure of soft and smooth, firm and full.
Clamping the bristles with your fingers, gently comb down, check that the brush is easy to fall off.
Tap the brush in hand, draw a semi-circle, check whether the brush cut neatly.
Hot air brush in differentiating species: maintain the status quo for animal hair, curly hair is a man-made fibre.