Be very careful with the TW Rubbing Compound, it is often referred to as "sandpaper in a can". It can be very easy to go through your clear coat, especially on a bumper. If the deep scratches go through the clear coat the best you can do is touch-up paint.
ScratchX is made for use by hand, and here is a link you should read on using it, and also a link on touch-up paint:
http://www.meguiarsonline.com/forums...&threadid=1516 http://www.bettercarcare.com/articles.php?articleId=27