That is pretty much the same process I use, which makes sense wince it is based off of yours and Waldronates tutorials on his page
I think I found though that it would pay to actually work on the initial grey scale height map in more detail before going through the Wilburization which takes quite a lot of time. In particular getting all the ridges and lines in first hand. Not doing so I found I had to go back a lot to gimp to editing the height map before running it through Wilbur again.
Oh also if one is aiming for particular river routes to really set those down darker a few heights below the surrounding grey scale so the incise flow will head to them. and also ensure that they are a smooth down hill towards the sea or just make them entirely slightly above sea level.
Ozdarchangel that looks like the right workflow, but I suggest you check the
Eriond tutorial Arsheesh made and obliquely linked to, it is really good and useful and you'll learn a lot by doing it. I did.