Ist of all heres how to back tape your door apartures like this pic
Heres some close ups of what to do
Go around the door aparture with 2inch tape sticking it to the inside of the opening with the sticky side facing out.
Then lay your masking plastic over the top and press it onto the sticky surface of the tape.
Trim with a very sharp razor but dont cut right through the tape when doing this.
Next stick some 3/4 inch tape over the cut edge of the plastic so theres no chance of the plastic blowing around while your painting.
This should take care of all the openings on the car, do it this way, windscreen openings, boot opening and door openings.
Now if you want to protect your roof from overspray you can use the roof gutter line as a taping point.
Stick 2inch tape all the way around your gutter line on the inside of your gutter with the sticky side facing outward so when you lay the plastic over the car it will stick to it.
Cover with plastic and trim off the excess as before and run 3/4 tape over the cut edge as before also.
Should look like this
If you want to keep the majority of paint off your quarters you can use this technique.
Its call soft edging and is very effective at not leaving hard edges when masking.
First of all tear off an appropriate length of tape and fold about 1/4 of it onto itself sticking the two surfaces together, you should now have a piece of tape that is folded along one edge and the other edge is sticky.
Stick this along the rear door aparture edge making sure the non sticky area is aligned with the aparture edge.
Now you can mask away from the tape with plastic and cover the rear quater.
The front edge of this mask can now be lifted slightly creating a gap under the tape.
This gap produces a kind of air lock when you spray over it, it sort of blows the paint back away from the gap which in turn allows the spray to coat right up to the edge of the tape but not under it keeping it much tidier and a lot less overspray to rub before painting the outside of the car.
I use painters plastic in conjunction with waxed masking paper to mask up cars as all painters do.
Dont use newspaper if you can help it as the acrylic paint can soak through and start melting into areas that you are trying to protect.
Try and find a paint dealer that sells both its a worthwhile investment.
Hope this helps
Cheers
