Terrain Smoothing in Wilbur

[antillies]

Hi!

I have a height map that I'm trying to edit in Wilbur. Specifically, I'm having difficulty smoothing/lowering terrain so that it is of a more or less flat/uniform height (Image 1). I'm essentially trying to flatten said terrain so that it becomes a flat plains region.

I've scoured waldronate's tutorials and the forum at large but I haven't seen or have missed any specific instruction as to how to manually flatten/raise specific portions of a map.

I've messed around with the various brushes and though the "subract"/"add" behaviors do lower/raise heights, they do it in a more isolated fashion rather than in one that is uniform. Subtract, at least in my usage, seems to have a bad habit of "eating through" the terrain (Image 2).

Any help in this regard would be much appreciated. Thank you!