Ya the weathering was the last step, following the Rub n Buff. It looks best as a non-glossy paint (I haven't seen much shiney dirt in my time). The sponge was key because, although you can't see it in detail in the pictures, when you blot it, you can also wipe it a bit which adds really fine streaks. The streaks really resemble the swirl marks you would get when polishing metal and makes it look like the dirt got trapped in the swirls. It's pretty subliminal, but it has a lot to do with the look.
I can't wait to get more of my gear finished either. My time is limited so I can only put in so many hours here and there, but I am steadily moving forward. You are right about the accuracy thing with the custom. Thats the best part really is that you are free from having to do things a precise way, but at the same time there still is obviously a degree of accuracy to follow to get a good effect. Going custom, you have to also be careful to remain balanced and not over-do it. The design of Jango and Boba are really masterpieces from great artists in a galaxy far, far away. I still look at my 12" Jango figure and think "man, that sure would be a great costume..." but at the same time I am happy with creating a personal set of armor.