Hi guys,
I do have some AutoCAD experience and believe I understand the questions. I've only been using Maya for about 6 months myself. AutoCAD workflow is definitely different. The easiest way I've found so far for creating interior walls and then adding thickness is by using poly planes.

I create a plane the height that I need and rotate it so that it is standing upright like a wall. then I goto the top view and perspective views and start extruding the edges. I will use the rotate and the snap tools to get the precision that I need. Then I select all the faces and add thickness to the walls. It's worked quite well for me so far.

I've also created walls using the poly cube method. Works pretty good as well. I'll use the snap tool for placing the walls after creating them. I don't bother with trying to union them. I just let them overlap.