Used smokescreens for the first time in our game last night.  Noticed that unless I miss it, there is no rule for smoke dissipation.  It says you put the counters down, but doesn't say anything about when you pick them up.

We came up with our own expansion/variant on the existing smoke rules, that worked extremely well for us and "felt right."

Only destroyers a light cruisers are generally used for laying smoke.  (This actually makes light cruisers a little more useful and more effective in the role of a screening element.)

Whenever a ship lays smoke place TWO smoke counters in each hex it enters during movement for that turn.

At each end phase, remove 1 smoke counter from each hex containing smoke.

Shooting through smoke counters takes a -1 penalty for each smoke counter it must pass through to the target.  Smoke counters in your own and the target's hex count against this total.

If there are three or more smoke counters in a single hex, that hex blocks line of sight completely.

Torpedoes are unaffected by smoke, except where line of sight is completely blocked.