Teak Handrail Removal (Cal 39)

Well, since I've been crewless lately I decided to get an early start on winter projects and started removing my exterior handrails to let them dry out, sand and varnish them and fill the holes in the deck with epoxy. Thought I'd be smart and start with the aft port rail since it only had 4 bolts to see what I was in for. Well 2 of them broke, 1 took over an hour to get out and the other took about 20 min. This doesn't bode well for the remainder of the rails! Question: the bolts are still sticking out below deck so I've bought a set of bolt removers that you pound onto the bolt and try to twist out. In this case I will be trying to twist them all the way thru the deck and out into the cabin. Should I heat them with a heat gun to try and loosen the grip of whatever is holding them in there tight enough to break the bolt? Anyone have an idea what might have been used to seal these bolts that is holding them so tight? By the way, I broke them by using a pair of vice grips for extra leverage on the big screwdriver I was using to remove them. The slots are so shallow in the bolts I could not believe I was able to break them. Hopefully the remainder don't give me as much grief. Thanks - Paul West Adventure Kwest '80 Cal 39