Adding a texture to multiple terrains

When selecting multiple terrains, Unity doesn’t appear to let you add or modify textures. Right now I’m just looking to add the base texture to a good number of terrains at the same time. What techniques are people using to do this? Should I be writing my own editor extension? Is there some short cut I’m not seeing?

Issue is I’m importing a large number of height maps from SRTM and other sources, and will end up with thousands of unique terrains. Clicking on them one at a time to add a base texture is impractical.

If anyone else ever stumbles upon this, I was able to accomplish this using Multiple Terrain Brush 2.0 asset from the asset store.