Some excellent work there yourself, Dave! I can just hear that door creaking as it's wrenched open! LOVE IT!
I'd say you've got a pretty good thing going already--you have some great results there.
Dullcoat is a pretty "toothy" finsih, so it would take weathering effects very well. A lot of these guys who use Future on top of their finishes don't undersatnd when they can't get good weathering results. You need that flat finish,
I guess your next move would be to experiment? MIG has a nice "Oil and Grease Stains" premixed wash that I just picked up. Good luck in your endeavors!
By the way, you might want to check out my Nomad here on the site if you're a subscriber for some "uber-weathering" tips!
http://www.finescale.com/fsm/default.aspx?c=a&id=3207
and...
http://www.finescale.com/fsm/default.aspx?c=a&id=3208