Comfrey, I just either dig mine into the ground at the end of the season, or compost it with everything else
Putting it in water, shudder from the memories of the smell
Any reason you put a roof on your composter? Most now recommend not to as it easy for it to dry out. I tend to agree, we inherited one years ago on our allotment and after a year it had hardly done anything as it had dried out from its own heat and the cover stopped any rain water getting in. Ours are now open and rot down well. This time of year if it goes a week without rain I put a watering can of water through them as you can tell they are getting dried out.
I havent tried it yet, but one of the guys at our allotments is using rhubarb leaves for keeping pests off. Hes putting the leaves in water and letting them rot, but Ive seen people say just to boil them for 20 minutes and its as good.
They say not to put them on food crops, but like anything a small amount I am sure is fine.
The other year I did put the leaves directly on the ground around some plants and the amount of bugs on them was low, but not zero.