careful teardown and cleaning is recommended.
I remove knobs (take note of what goes where) and wash them in the sink with the cleaner of your choice and hot water. I use compressed air to blow off the water and make sure they dry well and don't rust.
you don't want to go at the thing like a gorilla
I try to disassemble the front panel (if possible, on dmm meters its not hard, for example) and then I clean the whole panel once the pcb and insides have been removed.
de-oxit is the only spray I'll use (#5) when cleaning switches. avoid no-name radio shack style stuff.
sometimes taking the thing outside and using compressed air is enough to clean the insides.