I thought I've seen it all!! I'd pull the plugs and spray wd40 in the cylinders so that it'll have a light coating of oil to prevent rust.
some people will even get the oil can and squirt in there but at least with wd40 you can cover a larger surface area within.
Dessicant is an interesting idea but once in gets saturated with moisture it wont be able to absorb any more. If you buy a can of wd40 it'll cost you $3.00?? vs. $32. While your at it remove the rocker shafts so you dont keep the valve springs compressed over a long period of time.
14mm for the older CB heads, stock and many other aftermarket head but lately the newer cb heads use the motorcycle 12mmm plugs.