I have some problems with /b over brush
Everyone says that when you use this with gunpowder it supposed to create a new layer of blocks, however, for me it works similar to the arrow (replacing blocks)
Does anyone know how to make gunpowder work like I want to?

Currently it is either a bug or an unupdated feature.
Gunpowder will work with /b erode ? Brushes but it will act like an arrow on thing like /bb or overlay.

To put it short blending and overlay are broken for gunpowder as well as other performers i think.