Usually welding a few beads around the inside will shrink them enough to get them out. If that doesn't work then your next best bet is to use a torch to cut then from end to end on one side and cause them to collapse a little. The last thing to try is pulling them out with a threaded rod, alone and/or with a hydraulic, through hole ram. The problem there is that this typically only works when you've either welded or cut them first.
As far as putting them in goes, dry ice will work just fine. The main thing is to let them set packed in it long enough for them to reach the temp of the ice completely through the bushing, otherwise, as JD seller said, they will expand back too fast to get them all the way in. One way to help the process is to stick them in your freezer overnight before putting them in the dry ice so they don't take as long for the temp to drop enough to get the maximum shrinkage. Even better than dry ice is liquid nitrogen. Over the years I've put in bronze bushings as large as 8 inches in diameter, and steel ones up to 6 inches or so, with it, and used dry ice on items as big as 4 inches in diameter and about 6 inches long with no problems.
Again, the main thing, when using either the dry ice or the nitrogen is to let the bushing cool all the way through so they don't get halfway in and stick there. Good luck.