Help with Brushes!!

When I activate one brush, the active DRAW tool and I will customize my model with the brush, it comes out with a horrible quality, horrible even to the point of not be a difference of a Brush to another.
How is:

(•)Invert [X]

Only in PAINT MODE (with the PAINT BUMP tool), when I increase the size of the border it is less ugly, but still traces remain with a poor quality:

Another Brush (Giraffe skin):

I watched a video of a person doing the head of a dinosaur (I’m also making a) and used the Brush effect to create scales, since me out with this poor quality. Can someone help me? I’m new in the program and enjoyed the creative freedom he has!