I've used the brush on masking solution before...it's kind of like a low-stick latex glue. I got mine from an art supplies store.
There's a few caveats...
1. Personally I wouldn't use a spray-on version, as you'd have to reverse-mask everything with tape before you sprayed it, so it won't save you any effort.
2. It doesn't stick too well to glossy surfaces, so you've got to work out how to key the surface somehow.

I had an old '29 Ford with the 'Ford' letters on the tailgate. I painted the whole truck in a cream color, and wanted the Ford script to be white. It worked out FAR easier to paint the whole thing, and then carefully brush-paint the raised letters afterwards with a signwriting enamel (I used One Shot (about $7 a can)), with no masking. You can easily wipe off any over-brush while it's wet, and it gave a perfect result.
The letters aren't big enough to show marks or orange-peel.