I have never tried this but i do remember chiping some paint when i put mine together. So i was thinking maybe you could put a strip or even two strips (one on top of the other) of masking tape along the edges of the doors and fenders.
I simply use masking tape around the door and the areas it will be matching up to. I leave the tape on the door until after the front fenders are in place. I have done the same when putting the hood on and will also lay some towels over the top of the cowl area.
Why are you painting your car in pieces? Your opening yourself up to all sorts of paint damage when you put the car together. Taping edges and top panels is a good idea, but a bunch of extra work. Also, you will run the risk of not mixing your batches the exact same. I have a newbie high school kid working here in the body shop part time. He made that very mistake just last week. He sprayed both fenders, mixed up another quart of basecoat and sprayed the hood and bumper with it. When the car went together, the fenders and hood were a few shades off from each other. It was not noticeable until the parts were put on side by side. Mixing paint is not always an exact science, even with this fancy mixing machine and scale.
I would suggest the following procedure:
1 Jamb the entire body. ie inner trunk, floors,firewall, etc
2 Cut in the door jambs,door shells, bottom of the hood and trunk.
3 Assemble the entire car and include all outer panel painted surfaces.
4 Spray the entire outer body.
We have been using this process here at the bodyshop for over 20 years. It's the best way to get a good color match and not tear up your new paint job when putting the car together.
Just my 2 cents. Nicholas
I painted my car in pieces but it is a solid color. I wouldn't paint the car in pieces if it was a metalic paint or pearl. I didn't get one sratch on my car when I put it back together and my car was stripped. I rebuilt everything. By painting the car in pieces I got much cleaner work when spraying the parts like no over spray. I know no one will ever see most of these ares but I know it's clean.
The car I just painted was done some what together. The head light buckets and other front end pieces where painted off of the car but those will and do match fine on. The hood trunk and doors where hund on the car because the paint is a metalic paint. You can see pics on my web site. The side vent pieces where painted off of the car and they match great when held up to the side of the car.
If you have to paint the parts off of the car then you must spray them with the same mix and at the same time and hang the parts like they would be on the car if they are fenders or doors. If you lay a fender flat it will more than likely not match even if you spray it from the same mix. You also need to spray the parts the same time you are spraying the other pieces. This will take out any other condition that could cause the color to change.