-dilluted dish soap
-simple green(can buy at walmart,kmart, pretty much anywhere)
-rinse water
easy, just a mild dish soap dilluted in a bit of warm-hot water. Just dunk the rag in te dilluted soap water,ring it out (it should be a bit bubbly), and then rub the spots a little. After rubbing with dish soap spray a bit of simple green on the spots. Rub with the same rag and they should come off no problem. After that use rinse water and a different rag to wipe the area.
after that i would apply some vinyl/leather conditioner and protector.
let me know how that works for ya.
-walter