I work in a car factory, and its normal to bend all the doors into shape, twist the tailgates into shape etc etc.
We just do it with the windows up aswell, and havent broke anything yet, and thats doing it to 400 cars a day for the last 10 years or so
Just close the door onto your foot at the bottom(steel toe cap boots) then just push the top of the door in, or rest a rubber mallet between the door striker hoop and where the door lock is, then push it in that way etc etc. no big deal