Where do you feel the blockage? Up around the ribs or sternum area, down towards the rectum, more towards the left or right, ...?
If you're taking Julia Chang's herbal advice, she recommends you finish at least one bottle of the GCG before flushing. However, she does give credence to using Epsom Salts during a flush for those with very congested livers, first time flushers, or people who didn't get out (m)any stones during their first flush. You may want to do a Clark flush after finishing the first bottle of GCG and see if that doesn't help get more bile flowing to help with the constipation problems. The oil from the flush may help as well.
I originally got the salt water flush from the MC, actually, so you may want to check further into doing a few while on the flash. The gentle yoga-like motions really help me get more 'gunk' out.