Good thinking, never really tohught about washing the keyboard! but given what you are saying I really should!
You can wash your keyboard by disassembling it completely ! But its not a good idea, it can work weel even without it ! I once tried it but its tideous, assembly and disassembly !
i am the only user of my keyboar so i dont think that my pc have lot of microbes. But i am cleaning my keyboard and screen dust with cotton every weak.
Interesting fact but I never wash my keyboard and mouse. Compressed air and wet cloth seem to be good option.
just wipe the dust every random time... usually when it gets darker color... sometimes once every 3 month hahaha..