Get a little simple green solution and put it on a rag soaked with warm water. Put the simple green covered rag on top of the sap and leave for 20 minutes. Come back later and simply wipe away the resin!
I take my car to a car wash, and if that doesn't get it all I have tried putting dish detergent on the sap spots, letting it sit a while, and then scrubbing it off with a warm, wet rag. Goo-Gone works too.