I stumbled across something cool today. I have been working on a huge cluster of 6x6 regions, with all mis-matched, imported terrains. So there was a LOT of terraforming and blending, which can take a long time with the land tool. I discovered a debug setting "LandBrushSize" It normally maxes out at 11, but you can set it to cover a HUGE area and very quickly flatten out sim edges and smooth them, build mountains quickly, etc. You can get to the Debug settings with control-alt-shift-S and type "LandBrushSize" in the search box. It set mine to 30 or 40 to do large areas.