We have just done ours.
The whole unit was held on by three metal clips. To release them just press the long "tongue" at the back, it's best to have someone holding the unit while you do this.
Carried the lot out to the washing line where we tied it up with plastic cable straps.
A sponge and hot soapy water soon cleaned the dirt off and rinsed with a hose. They were left to drip dry for a day and then clipped back into place. As good as new
depends what they are made off - my kitchen ones were wooden and i did as dilligaf suggests but they were left slightly water marked, don't think would do it again