Seriously, matching silver is no easy task, and to do it right on a bumper will require the use of a flex agent. However, if it is a fairly small repair, the touch up information on this site will provide an adequate repair. If the scuff has caused the plastic to be roughed up, I would suggest carefully sanding the affected area smooth before painting. Also, remove all wax and sealants around the area before painting. Good luck.:xyxthumbs