I've found the best way to clean these boards to be a dishwasher. Pull out the RAM/ROM(if in chip form) and basically any other item that can be removed and run it through the dishwasher with a tad of handsoap(or any non-oxy/variant thereof). Then, let it dry for a minimum two days(week=safer), and see how it works. Also, this gives the benefit of allowing you to see which capacitors are still leaking.(Though, it'll probably take a while for the culprits to make a large-enough-to-be-visible mess)