I made a landscape blend using a splatmap, etc, which works fine, but then I added another layer and tried to paint on some sand around my lake and it makes this really weird black/gray material seen in the picture below. I can’t for the life of me figure out why this happens instead of the sand just blending with my other blended textures. Any help is appreciated – thanks!
Could you post a picture of your material + have you created a layer for the texture that you want to paint? (the little “+” beside the layer in the paint mode) 
do you have one of your layers set to alpha blend and the rest set the weight? You’ll also need to paint over the whole terrain with on type (don’t ask why). just get the biggest brush and go over the whole thing once.
I tried to set the layer I want to paint on as an alpha blend, but it is really blocky and unorganic. How can I paint onto my landscape without it getting “blocky”? Thanks for the help so far.