Next time a vehicle comes in like that, pull the seats out and spray a ton of degreaser on them. Then take your pressure washer to them. Its amazing how much better they will turn out than even a full blown extraction. When they're that bad, you can't really be concerned about damaging them anymore than they already are. Shop vac all the water out and then either leave them in the full blown sun, or buy a commercial air mover/dryer and put the seats infront of that for a half day to a day.
This should net a perfectly clean seat every time. I've even gotten welders muck out of a F150's seat before.
Otherwise, the exterior looks great, no holograms or anything, bravo.