Trouble installing new shocks.

So I just got 4 new Bilstein shocks and the front ones went on just fine. However, I am having trouble with the rubber on the rear 2. The rubber is making it hard to put the shocks onto the bolts attached to the car. They seem too tight to get on. I have tried grease and freezing the rubber, but it still won't go on all the way. How can I get these on? Thanks