Honestly, the easiest way I found was to don the tanks right at the back of the boat and giant stride in... Trying to don tanks in the water with 4-6ft seas would not be fun...
Coming up is a different story, a short down leash is nice for clipping the tanks to when coming back up... unless diving a single AL80, in which one can easily walk up a ladder just like all the other cattle...
In my case, donning two tanks before going in is not an option. I suspect 4-6ft seas will not be, either.
Has anyone hung their tanks or had them handed down? I am unsure of the hand-down method, as it seems I might be blocking others trying to get it. Also, the boats I dive want the doubles divers in first.