At a local paint jobber you can find a two part epoxy mix for bumper (small) repairs. It is expensive relative to JB Weld. $12-15 but the stuff is outstanding.
Just a scuff, dig or small crack? This stuff is the bomb.
SEM 68422 Bumper Repair
Beyond this I believe is the two part pro stuff and I think there is heat used in the application. Sub $500 to get equipped but for one job? Nah.