Had some bird **** on my car today, it was probably only on the car for no more than a couple of hours. I came home and washed it off, however, there is now a stain left there, looks like the acid of the **** has left a "burn" mark in the paint. I've had this a couple of times before on previous cars, makes me livid! What is the best method for removing this stain? Or will it remain for ever more? I tried some AG Rapid Detailer on it but that had not effect.