Alpha brushes landscape paint

In this video, paint a “perfect” alpha brush, but in my terrain is bad. tutorial please?UE4 Landscape - Painting with Alpha Brushes - YouTube
My brush does not paint with that detail help

Your terrain has to be detailed enough to show little differences like in the alpha brush.

detailed diference is a more quads? or more resolution image? or?..

Both could be limiting factors.

If you scale up your brush radius way bigger, does it end up looking sharper when you paint with it? If so, you are limited by the terrain resolution. If not, maybe your alpha is just blurry.