I'd just vacuum the card slots and wiring side
with a shop
vac with a crevice tool. I really would not get it wet. If
you do this, vacuum all the water off and then dry in an
oven at 100F or so for a day. You can clean the card edge
fingers with an alcohol-soaked paper towel.
Yeah, if you can avoid washing it, so much the better. Don't be too afraid of getting
it wet, though -- I've washed many Unibus and QBus backplanes. I use dish soap and hot
tap water. I used to dry them in the kitchen oven, but now I've got a hot air drying
rack, which I believe was originally sold for drying litho plates. If you have to use the
oven, leave the door ajar and set it at the lowest setting.
Thanks,
Jonathan