weird things happening when painting on a landscape

the landscape painting layers are pretty unintuitive at best but i’m starting to figure them out. One thing that is really weird is that when i put down a layer 2 material (dirt) then a layer 4 on top of it (mud). when erasing layer 4 layer 2 is under it, as expected, but when i go to erase layer 2 layer 4 comes back… is there another way to erase? right now the only way i see to erase is shift click,

Also i cant seem to get a smooth line, jagged as if the mesh is to low res but doesn’t line up with the polys underneath.

Any ideas, workarounds or tips?