[Heddy]

Hiya, it is better in my opinion to spray the whole thing, but I'd only do a bumper. Best thing is to swap for another, but finding one in as good or better condition is hard. I sprayed my front bumper all over using a custom spray from Halfords of all people. I primed it, flattened it and sprayed the top coat. I then lightly flattened it with very fine wet and dry before lacquering. I'm happy with the results, but if you're going this way then you really need a warm calm day.