I paint them in Unreal yes. Basically my Material/workflow looks similar to
My models have a higher vertex count whever different textures meet, i.e. pathways or cliff/grass connections, to allow blending on a smaller scale there. Since my models are pretty huge for terrain, and the brush size seems to be a value based on model size, I frequently have to turn it way down to 0.1 or 0.05 or something to only catch a few vertices or even only one at a time.