Question - Optimal way to texture blend (landscape paint)?

Having trouble blending 2 layers in landscape painting. The falloff setting or tool strength doesn’t seem to affect the transition. Wanted to get a smoother, longer blend of the two (in the example, the sand and dirt).

Any idea on how to achieve this?

EDIT: I added an Edit layer and created a second transition, but when I do that grass blades appear in places where they shouldn’t so I cannot use this technique with layers that have them.