One of mine was a bit stubborn. Started out with a 3/4" x 6" round pin and a 3 lb. shop hammer that worked on the right side. After about 10 minutes of hard hammering and 1/4" progress I sweet talked my bride into helping. With the drift firmly clamped with vice gripes, she held it in place. Then with both hands in play, it only took about 4 or 5 minutes to drive the left side pin out. Using the hammer with both hands made the difference.
A 5/8" (or was it an 11/16th ?) impact socket was the perfect size to push the bushings out on the 30 ton press.
RonR