+1 for Floor Jack + Towels + 6x6.
2007 - 10 years of Chicago winters never removed doors until this summer.
Placed 2 flat stack's 6x6 on top of each under the floor jack put at least 6 inches of rolled up stacked towels in between the door and jack. with the doors opened halfway jacked up slowly until i got to the bottom of the doors with some pressure and rocked back and forth. sure enough they came off pretty easy that way. Used some liquid wrench and WD40 as i was doing it. I put the top of the jack at the bottom of the door as close to the hinges as possible.
Replaced all the inserts with delrin sleeves. Banging out the old sleeves was a whole other issue.