Start by clearing the car’s surface of any other debris like leaves, dust, and feathers. Then rinse off the surface with water. Afterwards, spray some cleaning formula like a detailer onto the surface where the stains are. Dab a clay bar onto the surface and keep doing this step as often as needed. You can make the most of the clay bar by kneading it well so you get a clean surface that you can dab onto the surface.
Once you’ve removed the stains, rise the surface with water and dry it with a car cloth. If you notice that there are still stains and marks that remained on the surface, use a special solution that’s strong enough to get rid of hard to remove stains like walnut tree sap. Then dry the surface with a microfiber towel. You can also do the added step of applying wax to the surface and then buffing it off with a microfiber towel.
You can use the Nanotech car polish compound available to easily get rid of walnut stains. What’s great about this product is that it’s also effective in removing stubborn watermarks in your car’s paintwork.