One blending trick in Wilbur is to load the DEM with sharp transitions and then:

1) Texture>>Gray Maps>>Relative Elevation. This process will select sharp changes in altitude.
2) Texture>>Transfer>>Texture to Selection will transfer that image that marks sharp transitions over to the selection.
3) Select>>Feather with a value around 1 will smooth out the transitions a wee bit.
4) Filter>>Blur>>Gaussian Blur with a value around 2 will smooth out the edges.
5) repeat as needed

This technique is basically a poor-man's edge blur (only edges are blurred). Inverting the selection between step 2 and step 3 will blur everything but edges. It goes through the selection, so there is a bit of clipping because the selection has only 256 possible values, but it's usually not too bad, especially after a few iterations.