Rent a carpet shampooer from Lowe's or Home depot, with the couch cleaner tubing attached. But fill it with a 1/10 mix of Awesome furniture cleaner from $0.99 store.
10 parts hot water.
I read all this on a thread on a forum. Everyone said they looked like new when done.
Fulltime livin' & lovin' it in '94 Bounder 32h.
Chevy 454ci Retire in 3yrs.