So far, all that's been mentioned is wrapping and the spray on chrome. Sounds like the wrap doesn't work too well. I have had experience with spray on chrome, parts I had done don't hold up well after time. It doesn't have the same color as chrome. It WILL turn yellow, and usually has a lot of dust in it. Especially on larger parts, such as bumpers being discussed.
There is a chrome shop that can actually plate fiberglass with REAL chrome. Paul's Chrome Plating in Evan City Pa. The process uses a copper base that can be applied to fiberglass, then electroplated nickel and chrome! I have no idea what they charge for this. They are not cheap. They are a very high end user kind of shop. Show car work. If you want your glass bumper to look like chrome, then use chrome! This beats the heck out of spray on crap!
Here is a link that was featured on a tv show. (My Classic Car) then click on link to Chroming Fiberglass on right hand side of your screen.

http://www.myclassiccar.com/episode/20/18/