Spawn grass on Static mesh per material assignment

I work for an arch viz studio and we have been doing a lot more projects in Unreal recently. A recurring issue is the flexibility of the foliage tools when it comes to painting on static meshes. In particular, when we model out a surrounding hardscape we have meshes, typically within curbs, with our grass material assigned (see attached image). Since these are not landscapes, there is seemingly no simple way to either spawn or paint grass with the foliage tool only onto that material without it overlapping onto other meshes. If anyone has any ideas that could help it would be greatly appreciated.

Did you find a solution?