This is one of the reasons why it's very important to protect the finish of any car.
Protective coating such as sealants, waxes, and the new Nano coatings provide a barrier so these little pesky's innards won't become fused to the paint. This of these coatings as sacrificial layer. An additional is they make the removal of these suicide runs much easier.
If you do happen to fins a manual car wash the high pressure wand should make short work of these. Another alternative is to stop into a WalMart or local auto store and pick up some wash, a bucket, and a sponge...