Yeah, hate to say what everyone else has said, however, you have a few choices.
1.) take it to body shop, which sounds to me like you're hesitant too... and for good reasons.
I lived in the UK for three years, and man your parking spots are tight at the old "pay-n-display"...
It won't be long before something gets scuffed or dinged again.
Option 2.) as mentioned above, Dr. Color Chip.
Here in lies the problem with the scratch, if it's through the clear, it's pretty deep. Any attempt at compounding/wet-sanding etc... will only remove gobs good paint that surround the scratch. If you were to hit it with your Flex, my suggestion would be to compound and polish as you would normally. 6 to 8 section passes over the 18"x18" panel. This will level things out but keep it commensurate with the rest of the paint. You'll notice that I didn't say stay on the scratch... Problem is if you do, you'll generate a lot of heat, and again, remove gobs of good paint.
Go over the area, 6-8 section passes. Then fill in with Dr. Color Chip. Wait a day or two for the paint to cure then come back and do another 6 - 8 section passes on the 18"x18" section and this should level out the Dr. Color Chip.
It won't be perfect, but should be able to pass the 3' test.
For the bumper cover, you can do a squeegee method on the bumper cover.
Here are some galleries of similar type repairs I've done where a bodyshop was out of the question.
Heavily Rock Chipped E350
Bumper Cover scratched by sheet metal
9 Year old Bumper cover that was at the end of it's life with 140K miles
Like I said, not perfect, not intended to be.
) I found two problems on the body of my car.
