@oncehandsome I make nearly every major component of the map in Gaea. This includes the terrain, the texture masks, and the map-wide decals. I've been experimenting with making custom textures in Gaea as well.
The texture masks sometimes get adjusted a little bit in the editor, but those are mostly details. The rest of the process, like placing smaller decals, mex layout and all the related stuff is ofcourse done in the editor.
As part of the tournament, I will also document my workflow and create a forum post about it. I'm trying to complete that map now, but (barring the unexpected) you can expect that post sometime this week.
Here's Project Dust as seen from Gaea:
Which, with textures and some small edits, looks like this in game: