Duct tape is thicker and stronger than masking and will protect your paint better. It will then trash your paint when you remove it. Masking tape is liely enough but if you're really anal. put masking tape on first, then cover with duct tape.
If you have one, I'd use a shop crane instead of a floor jack. wrap the whole door with a heavy towel or mover's blanket. then wrap it verticly with two heavy duty ratchet straps a third ratchet strap running through the first two will act as a pick point. with the weight suspended from above the door will be much easier to align. even the scrawniest of girlfriend's can hold it in place.
also, if you haven't got one already, grab a door spring tool from Harbor Freight. saves a headache later on.
hope this helps.