Any short-cut other than full removal of the bumper and refinishing will result in some sacrifice on quality. That doenst mean that your only option is 100% or nothing.
-Anything from a rattle can I've never seen look too nice. You may cover the scratch, but the blend with the remaining bumper will never look right. High potential of making it look a lot worse IMO.
-Blending only a corner of the bumper professionally, or "blowing in", will achive the right clear-coat and shine, as well as allow you to fill in the depth of the scratch with some product (if needed).
-The downside here is again, the blend to the remainng bumper is tough. Misting the clearcoat over, with no solid vertical lines to cut off that corner can be hard to wet-sand and buff 100%. Also painting on the car involves the obvious masking or remining car & imperect lines where bumper meets tail-light, 1/4 or trunk lid etc..
My opinion. Overhaul and clear the entire bumper on the car. Remove all chips/scratches/ imperfections and do it right. This is a good balance between quality & expense. (saving money not R/I bumper)
Option 2. Get proper touch-up paint. Not a rattle can, and patiently fix-up the bumper. Save your money for when you find another scratch that makes it worth doing the whole car.