Most effective way is boiling, I use a little Oxy-clean or similar white-powder type cleaning product and sprinkle it all over the shamrock before I pour the boiling water on. If u gotta dishwasher, Cascade may do the trick ??

yeah, it'll stink so don't do it if your 'rents are around! And it's "gross" whatever, it's cleaning all that resin and crap off... would you rather be smoking it?! bleh