Really awesome tutorial Arsheesh...though I have to admit I was pulling my hair out with Wilbur, mostly trying to get rivers where I want them. Just wanted to show what I was able to do. First, I started with a CC3 map I made for some folks on G+ just for kicks. I wanted to replicate this map, but give it a more realistic feel.
Taming of the Eastlands 500x400 COLOR.JPG
Obviously, you can tell its a CC3 map a mile away.

Using your tutorial, this was what I was able to do:
TOEL2.jpg

I'm really impressed with the results. Obviously, I'm still not done. For example, I'm going to have to manually add some rivers in the dark "blob-ish" swamp area in the south. The trouble I was having with Wilbur is that it wasn't making good rivers...it kept making these terribly short "wisps". My solution was to go back to Gimp and tone down the Land Clouds layer (reducing contrast) and doing a little more sculpting on the areas I wanted to force rivers. The only place it really didn't work was in the south swamp area, and the southeast peninsula where you can see a bit of a rut moving nw to se. Also, I probably should have spent more time beefing up my mountains, they look a little sparse and thin.

Anyway, I wanted to personally thank you for taking the time to make such an incredibly detailed tutorial. Any chance we can get your techniques on labeling? LOL, that's my next step.