Hard bird poo comes off with a sponge soaked in warm water left on the stuff for a little while, I'd try that first.

That does work a treat, been doing it for years, normally use a piece of wet kitchen roll to be honest, sticks to vertical surfaces better.

As for sap it does not work. Bought a car some years ago and the paint on the horizontal surfaces felt like sand paper and the wipers simply made a mess on the screen. Dealer wanted to power polish it, I said I would consider it knowing it was the last thing i wanted doing to the new purchase.

Tried polish and T-Cut, both no good, tried white spirit, no good, tried meths, no good. Chap at work told me about clay bar so I bought a Meguiars kit (included bar and lubricant) and tried it, only a tenner. Brilliant. Paint smooth as glass with no effort, glass smooth as glass with no effort. Did the whole car in a morning then polished it using Meguiars polish, well worth the time. Always used Meguiars stuff since.

But why did the garage not know about this, turns out all body shops use it?