Years ago I used to use a KEW wet vac when we had the garage for doing the valeting,problem is if you get them to wet car condensates up and a wet arse even with the stupid plastic seat covers.
Since them days I have done set of recaros I got from my mates scrappy with fairy liquid and a pressure washer.Took aaaaages to dry out but good results.
The best result ever was seat strip down and shove in the washer.Take note if you do this you will have to give the door cards a good scrub but I doubt you will them looking the same level of cleanliness as the seats.I did all the rear and one front and then left 1 rod in one of the covers.It ripped the seal on the washer door and buggered it .I didnt dare use my mums brand new washer for the remainder
They looked very clean though