Are you talking about painting the bumper cover or the 3" black impact strip itself? Either way, look in the chassis manual and find the section on bumper removal. THe bumper cover has to come off of the car and then the impact strip gets taken off of the bumper cover.
Believe it or not, my wife hit a fox, trashed the bumper cover on the bottom end, and then, after I had sourced a vg condition used bumper cover from another lister, she had an argument with a chevy pickup over the same section of asphalt! The shop that did the repairs had never seen someone come in with collision damage with their own used bumper cover replacement. (We also needed a fender and paint work.)
BTW, I tried several boneyards for months, bumper covers and impact strips are vurtually unobtainable because they are a high demand item from shops and the boneyard usually will hold it and sell the whole front or rear clip.