Just use microfiber cloth moistured with plain water and wipe your camera body. Especially after come back from beach. Wipe again to dry it with another microfiber cloth. Yes, a lot microfiber cloth. And of course different microfiber cloth for body and lens/filter.
No special cloth or cleaning agent for me. I just wipe my camera with a moist cloth (but wrung sufficiently dry), the same type of cloth I use for cleaning my car's dashboard. After I'm done, I'll let the fan blow it for 10~15mins before putting it back into the drycab