I've always took a small drill bit to fit between the metal inner sleeve and the leaf spring wrap. This drills into the bushing itself. Drill several hole, all around, then drag the bit from one hole to another. You'll need a small stiff putty knife, a small flat screwdriver, little heat, lots of paper towels. You start to scrape the left over stuff as best as you can. Take some heat to the left over rubber, use the scraper to peel off as much as you can, and use the towels to clear the 'crap' off the scraper. This is a tedious effort.