Depending on the acidity of the bird's stuff. If it etches the clear coat, you may need Ultimate Compound. If it does not etch much, Ultimate Polish might get it off.
Yes, put a protectant back on after compounding or polishing.

You can take your 4:1 D115 and put it into a small spray bottle with a good lid and keep it in the car with a couple microfiber cloths. Bird stuff not only etches, it can lead to clear coat failure, so the quicker you get it off, the better for your paint.

Here is a good video from Larry Kosilla on best ways to remove bird droppings. It is worth watching.