One think to keep in mind for better or worse, is you can almost never get the stuff back off... I would make sure you are "done" with your project and it is they way you want it before doing it.

Also, if you are going to do a 'concourse' paint dab resto someday, you will have to remove it...

I used the spray can stuff after doing some welding on the wheel well and had one hell of a time getting it off when I went to fix the car "right"...

it has its good points, that is for sure...