Presure cleaner works but make sure its a hot day and position seats as flat as possible to dry, dish wash gets stains out and a quick hit with hot water and a scrubber brush ( carefuly to not chew up fabric) before a blast of with presure cleaner will get them as good as they can be.
Presure washer is good!, theres less water.
Also after letting em sit for 10 to drain away, a wet vac will suck out things and make em like new with no water marks.