Layered Physical Materials (w/o the Landscape Tool)

I want a piece of ground that can have multiple physical materials. Dirt, snow, mud, whatever.

I don’t want to use the landscape tool. The landscape tool generates enormous, flat, square chunks that don’t fit the walls, cliffs, buildings or structures that i’ve created within my 3d modeling software.

There is a paint tool that can create multiple material layers for a mesh, but it blends these layers based on the complexity of the mesh. This means I need an extremely high face count to get the blend to look crisp which feels criminal if i’m dealing with relatively flat surfaces.

Is there no way to simply create a material and have multiple physical materials that blend by way of, say, a mask?