The best way I have seen is to drip water down the bolt hole until it is full half way up the threads. Put some plumbers teflon tape on the bolt threads and screw in several turns.
Then when you feel the pressure of the bolt 'bottoming out' on the water, put an impact wrench on it. Since water wont compress (and since the taper end should be water tight) the pressure should pop it off the taper
