go to walmart, buy a can of like carpet cleaner stuff. idk what its called, but its red and has a scrubby brush on the top of the spray can. get some spot cleaner, and spray the seats(i did my carpet too) let it soak for a little while. then spray the seats with the spray cleaner and scrub scrub scrub. then use a shop vac and suck everything out.
my truck after i did it: