You can wash a keyboard in the top rack of a dishwasher with the heated drying feature turned off. Then allow to drain & dry. Make sure to seal up the usb or ps2 connection tight first. I use the tip of a latex glove and a couple of loops of a rubbermaid to seal up the cord end.
Alternatively, you can also soak it in a sink of soapy water. I prefer to use dawn as it cuts grease. Then drain & dry.
I have been doing this with all my corded keyboards since the 80's and works everytime.
Edit: Just re-read and you said, wireless. For a wireless I usually just pop the keys and clean it with
swabs dipped in alcohol or if it's really bad some goo gone.