harvest everything, pluck don't cut, any solid mushroom matter left on the cake can rot.
after the first flush:
i mix 1 part hydrogen peroxide (3% solution from the grocery store, cheap stuff) with 4 parts water. this'll kill some bacteria and provide water and oxygen for the mycellium. i mist the hell out of my cakes and mist casing enough that there's a little standing water in the bottom of my tray.
misting with straight water works fine too.
i've only dunked once, mostly because i don't do cakes. people do it all the time so it must work fine.
the point is to rehydrate the cake. i've even seen people put a straw in the cake and try to pour water into the center of the cake.