Thin mud and careful sanding, huh? My one attempt at drywall made it look like a topo map of the Alps. I had lumps where there should have been lines, and I sanded so much I created a new dust cloud in my living room. Let's just say I'm not allowed near the joint compound anymore.
Watched my buddy try to fix a wall once. He ended up with more ridges than a washboard, I mean it was bad. Now he just calls a pro, saves everyone the headache.