get a baseball bat ora tyre iron or whatever takes you fancy and push it in so it is sitting on top of the tyre poiting out of the guard. now kind of push the end down so it pivots off the tyre and the other end pushes against the guard. now get someone to either drive very slowly backwards and forewards or roll the car backwards and forewards.

But with that front part that hit I went axe on it before I did the lipping.. swearing and banging the crap out of it with a metal hammer ( No rubber mallets for me!) and I was surprised at how well it actually came out...