Just figured out that drawing using gestures in a limited ability environment like SketchUp, is only possible in theory. Practicalizing it would be a waste of effort.
If i go following the advice of NUI veterans Infrared Pen/Stylus should be the best way to draw in SketchUp. Design Wise it should look like this :-)
The thing is – fingers are great for grabbing, rotating, zooming. Big broad gestures. But drawing a precise line in 3D? Your finger blob is like 20 pixels wide, you can’t see what’s under it, and you have zero precision. I tried it on our table and it was just frustrating. A stylus gives you a fine tip and you can actually see where you’re drawing. Duh! Sometimes you discover the obvious only after banging your head for a week :P