If you want to carb it over a couple of days then around 15psi would be good if the corny is in the cold, longer if it's not in a fridge or a cold space. If you want to carb it overnight then set to 30psi(in the cold) or 40psi if not cold, purge and decant at 2 - 3psi. Now if you want to force carb it then get the beer cold and put the psi onto 30, with the corny on the floor rock the corny for around 15 - 20 minutes and you will hear the C02 going into the keg, put it back in the fridge and let it settle down for a few hours, purge and then decant at what suits your setup :small
thanks for the link to the washers.