Good timing on this thread; I just did a wheel scuff repair using the spot putty and Wurth silver paint this weekend.
It's much less hassle to simply pull the wheel off the car and set it up on a bench for the sanding and putty work. I had a light scrape about half way around a wheel. It's a simple process but you have to be patient. The putty has to dry completely before sanding, and the silver needs to cure at least a couple of hours before applying the clearcoat.
The Wurth silver is slightly darker than my CSL reps but by the time the wheel was back on the car you'd have to be a very picky individual to be bothered by it. I think the color would be perfect on factory wheels.
If you're handy with sandpaper and spray paint give it a try. I'd have a pro do really bad damage but for the typical scrape or gash this is a good method.