It appears that some kids enjoy tossing eggs and my car now seems to have some residue that won't come off with any conventional attempts. Any ideas on how I can try to get the remainder off the car ??

Thanks.

wetsand and buff

Wetsanding and buffing will work, but I would try a clay bar first.
It's a lot safer on the finish.
A good polish would be my first try.

bug and tar remover works well too.