I would use striping tape as Mike has suggested. The best (thinnest) stripping tape I've ever used is the Carl Goldberg ones. Not sure if they are still available
If you must paint the stripes, I have read a technique many years ago in one of the hobby magazines. For the AVL, paint the entire deck with the color of the strip first. In this case it is the dark blue. Mask and spray the light blue area. Then use fineline masking tape to mask the blue strip and spray white over it. Remove the masking tape and you have the dark blue strip. I have tried it in the past and it worked well. However you will end up with three layers of paint. I am also slowly building a AVL and my plan is to use striping tape.