Hard saddle bag question

[big stinkie]

Painting hard saddle bags for a friend. Bags have 3 long decorative indentations along the sides, each about 1/2 inch wide, 1/8 inch deep, running the length of the bag parallel to the ground. What is the best way to put a different color paint inside the indentations? Bags are already basecoated medium metallic blue with a coat of clear over them. Need to put a silver metallic base in them. Tried masking them off, but to hard to keep the edges straight. Looked pretty bad. Anyway to spray the silver without masking and then maybe somehow wipe off the silver with a sponge or something, leaving the silver in the grooves but removing it from the raised surface?

I think that originally there was some sort of chrome trim in the grooves. Does anyone know a good product to replace it if the painting angle doesn't work?

Here is a link to a page that has a similar bike so you can see the grooves of which I speak.

Thanks,

Kawasaki Vulcan w/saddle bags