Plastic parts that can easily flex - like a big wobbly bumper - need a flexerizer (not the real word, but something like that....) added to the paint so it won't crack. Adhesion on a bumper can be a big problem, too.
If you want to do it yourself then you're better off finding a local auto paint supply shop and talking to them. They can color match off the car and help pick the right products and layering so everything works. You probably don't want to spray a mix from the original color spec. Paint fades over time. After 11 years, "Ebony" is no longer "Ebony", so a match directly from the car is much better.
"Touch Up" is not a paint brand. So this is relabeled something, which is a red flag for me. If it's the bottom of the line high volume body shop paint, just put that on the can so you know what you're getting. That's not necessarily a bad thing, but it's better to know what the paint actually *is* so you can get the correct data sheets.
Buying paint over the net is fine - I do it often for some specialty stuff - but the supplier should readily provide tech sheets, MSDS, compatibility info, etc.
You've got a good respirator, strong compressor (15 gal would be OK for a really small job like this) and good filters/driers on the line, right?
