Reassembly of a restoration project always involves patience and attention to detail. One of the most difficult tasks to accomplish is replacing car doors without scratching or damaging the fresh painted surfaces. The two best tools for making this job easier are: masking tape and a floor jack.
Before attempting to mount your doors, gently adhere masking tape to the outside edges of the doorjamb area on the body. This will help prevent the door's sharp edges from getting nicked or scraping the paint off the jamb edges. The tape can be removed as soon as the door is mounted in place.
Now it's time for the floor jack. Car doors are quite heavy and bulky, so it is a big mistake to try holding one in space while aligning to the hinges. Even with a helper holding one end of the door, this job almost always ends up with damage. It's just too hard to keep the door aligned while fighting with its weight. Here's a better way.
Take a scrap piece of 2x4 and wrap it with a towel. Place the piece on your floor jack and raise the jack to the approximate bottom height of the door. Lay the door's flat bottom onto the wrapped piece of wood, taking the time to balance it. Now all you have to do is keep the door from falling off, which is easily done with one hand.
Position the jack such that you can roll the front of the door up to the hinges and then adjust the height until the door can be pushed into place. You will find this very easy to do because there is no physical effort on your part. This will allow you to be patient.
Once the hinges are roughly bolted in place you can lower the jack (keep it there just in case you need to stop the door from moving suddenly) and start testing the door for closing. You will have to move the door up and down slightly, as well as forward or rearward to get it in the proper position, and the jack will provide a resting place for the door during these adjustments.