You shouldn't need to rinse your risers if you don't get them soapy.
The dishwasher works well to clean motherboards and PCI-E slots.
.... really?
Yeah, of course. Remove all non-integral components including the CMOS battery, give it a cycle or two, then dry thoroughly. (The oven around 100c works well.)
I've not personally put a motherboard in the dishwasher, but I've heard of it, as well as washing in the sink. I have a dead ASRock 970-series board here that a Corsair H70 leaked all over which I will give "the wash and bake treatment" to see if it will come back.
I've done the oven trick to dry out boards after LN2 overclocking at -190c.
