Have cleaned plenty of these over the years. I'd suggest removing the mattress, covering the base of the bed with thick sheeting and removing the headboard and placing it on the bed base to work on. After doing whatever you need to do, re-fit the headboard and stand an airmover on the bed to dry the headboard off.
With decent extraction equipment and a powerful airmover you should be able to leave it touch dry, to avoid rust problems. If there isn't a problem near the studs, don't even get it wet round them, problem halved instantly!