Ok I am literally trying to paint a terrain I am using 4.7.0 and it is still painting the entire block when I click it here is a screen shot
://i59.tinypic/2gt22i1.png
Take a look at this thread: https://answers.unrealengine/questions/44879/can-understand-how-to-paint-my-terrain.html 
" As a temporary workaround, try painting with all of your materials while stopping to let each one compile it’s shaders. Once you do this, go back and try painting with each material and see if that works."
still can’t figure it out, this is driving me crazy literally almost an engine breaker for me.
Have you already tried what I suggested? -> otherwise send me your map + materials + layer infos so that I can test it with your setup. (you can also send it to me over skype -> )
I have tried it bro and I am either not doing it right or something. its insanely frustrating cuz its making me want to quit lol
Ok, the upper posted solution works