Al, the fine line tape which red linked you to is good enough and then go on after it with regular - however just overlap the fineline about half way leaving the acrylic fineline tape visible. Don't prep too fine as the sharp edge won't allow the paint to grip hold of the substrate and will break up as you remove the fine line. To add to what AndyB is saying some custom sprayers mask the pinstripe and then laquer, so that when flatted ready for its final clear coat it's one even thickness and you don't feel the ridge of the pinstripe. Our guys do this. Depending on what level of finish you want as well you might want to look at a 3000 or 5000 trizact or abralon pad before final cut and polish. (I can send you a couple if you want).
I don't mind the masking and the spraying............it's the damn rubbing down I hate.........I might be enough to put me off doing the whole job!
Many thanks to Sev for invaluable advice and some stuff for an awkward little paint job I was messing about with.... AL
@Arquebus , how did you get on? I might have a similar and really horrible job to do soon, although I'm trying everything else of I can think of to avoid it.
@Sev Is "3000 or 5000 trizact" a finer version of: Scuff Pads Abrasive Pads like Scottish Finishing Pads Grey Ultra Fine x 10 | eBay ?
Look in the SS gallery The Trizac pads are very fine and work well when wetted......I polished afterwards and it seemed perfectly OK..........Then I lacquered it which is really the wrong thing to do with no keyed surface, but then, I am doing it to an 18 year old bike.
You can use 1500 or 2000 grit. You only need to flatten the surface off and remove any nibs that might be left. After that clear coat and finish off with 1500 or at least no more than 1000 grit and then compound fully and polish.
Something like this? FARECLA G10 FINISHING COMPOUND LIQUID PAINT RESTORATION 500ml CUTTING G10-500 | eBay
I use G6 rapid and then G10 to finish. If you prefer you can use G3 and then use G10 which is very fine. I also use T cut on a mop which is good for something between G6\G3 and G10.