If the chips on the edge of the door are only on the edge and not round on the surface of it this may not work, this is really only for doors that are chipped on the very edge of it.
You will first need to flat it down, so all the edge is smooth and free from chips, don't panic if it goes to baremetal. You'll need to flat it with P800, taking care not to flat the outside edge of the door. If you in doubt run a piece of masking tape down the outside next to the edge, this way you will only catch the tape and not the paint work.
Once your happy it's all completely chip free and smooth, what you will need to to is apply and etch primer over the bare metal, you won't need to high build primer it as its only very fine flatting marks, you'll see in the pics how to mask it, with the etch primer will only need to be a very light covering coat.
Once your happy with that you can apply your colour, this can be done with either aerosol cans or spray gun which ever you have chose to use, once your happy with the colour and it looks right, just apply a couple of coats of laquer it doesn't need to be a heavy coat just nice light even coats.
The way it's masked which you will see in pics, the tape is part folded this cause a slight flap in the the tape, so when you spray it it actually lifts up slightly, reason for this is it makes it so you don't get an hard edge in the paint, once it's dry and de-masked you may see a slight edge to paint but this will easily polish so it doesn't show.
Trickiest part is mastering how to get the tape to fold over, you only need to fold it over by two or three mil, it's just practice and the angle you hold the tape, I tried to do a video clip to show you how to do it.
Any heres the pics on how it's done.
See how the tape edge has been slightly folded over.
Above is the inside the making tape has been run down in line with the bead of sealer on the inside of the door.
Above is how to run masking tape Down the outside, see how it's in line with the very edge of the door, but still enough do the flatted area can be painted, it's just keeping painting to a minimum spraying as smaller area as possible to save spraying while door.
Above gives you a picture of how the edge should look when masked and an idea of how smaller you doin.
Just a piece of masking run down inner edge, you'll need to do the same on the outside.
Above is the quick video showing his to fold the edge of the tape over hopefully it's worked.
Hope this has helped to show how to do it.