Step 1: Set Up
Scissors, a sharpie, a screwdriver, pliers, a wrench, a bunch of rubber tipped clamps, a metal spackling tool, weights (dressmaker's will work),
a 2-3" paint brush, rags, some newspaper or a drop cloth (this gets messy), Barge cement, and Barge thinner and a ventilator is always a good idea when working with strong adhesives.
Purchase 24" x 24" x 1" Foam and head to your local Auto Upholstery supplier for a yard of perforated vinyl (headliner material).
Step 2: Remove the Seat
With your flat head screwdriver, pry up the small metal tabs around the perimeter of the metal chair pan, releasing the old upholstery.
Step 3: Remove the Old Upholstery Fabric
Step 4: Remove the Foam
Put on your respirator because it is time to get agressive with the metal spackling tool. Saturate the foam with Barge Thinner and vigorously scrape as you go. Most of the foam will come off in bug chunks. Then dampen a rag with more thinner and rub the remaining foam and adhesive away.