I prefer to sand the whole panel rather than leave a clear edge around the graphics, unless you plan on a pin stripe around it. You can use a gray scotch brite, or 600 wet or dry with soap and water, followed with a paint prep solvent wiped with a lint free towel. Tack and paint. Clear whole panel after. the clear will cover any 600 scratches.
If it's not dull, it's not ready to paint. The shine will come back with the clear.