Dawn and Lava bars.
Better yet, keep some hand scrubs with your tools, when you finish the job, scrub your hands with the wipes/scrubs and remove almost all of the junk Before you go into the house.
I have used both of these, and they are great;
http://www.zep.com/ZepSearch/default...xact&country=U
http://www.dymon.com/dymon-product.php?product=1177