Do like I told ya
Spray the whole caliper with the base color you're going to use, like White.
Go by any graphics shop, have them cut the AMG logo for you out of vinyl, only in a negative (so instead of the letters being individual, you have one "strip" of vinyl with the letters removed). Use this as a stencil, spray the green paint, and remove the vinyl stencil after you're done spraying. Once that dries, spray with clear, and bake.
Honestly, I wouldn't even mess with powdercoating. Any good paint shop should be able to obtain high-temp paint...