I've done this manually with Meguiars cutting compound and repair polish, but it takes a while by hand. My Golf is red, and the paint reacts very badly to bird poo.
I always carry a bird poo kit in the Morgan, and needed it at RFTH as we were under a tree and got a pigeon sized dollop on the front wing. It was still moist when I found it and so it wiped off and didn't leave a mark.
On holiday at the coast I'm super vigilant.................
