The 1968 Body By Fisher Manual, Section 13 "Folding Top", page 13-29 to 30 has a good description of bleeding the convert hydraulic system. If you don't have one, the Team Camaro website has one online. See: http://camaros.org/forum/index.php?topic=9433.0
It's a simple bleeder system but you could purchase Ames part FH379 to keep from having to round up the items needed to do the job. It also has instructions.
