I used two blankets, we sewed them on with a thick thread that looked like rope but I would compare it to about 80 lbs fishing line but made of thread.
I suggest getting some kind of eyelets and punching them into the fabric where you plan to run the thread, that will help the material from tearing as the thread gets pulled. Then we centered the blanket on the seat from side to side, wrapped it around the back to make sure it reached everywhere and sewed it up and to the seat springs. I didn't remove the material that was on the seat, just put the blankets right on top of the old vinyl or leather what ever that was.
Good luck and I'd love to see pics when you are finished.
