I use an old standard sized plastic dustbin which has a capacity of (I think) 80 litres. In the base I drilled a hole about 1cm diameter.
On the inside, over the hole, I placed a small 'dome' made of chicken wire. This allows the liquid through but keeps the solids from blocking the hole. I kept the 'dome' in place by sticking it down with gaffer tape.
Placed the dustbin on top of a bucket, chucked in plenty of comfrey leaves (I have 22 plants) but tried to avoid stalks. Kept the lid on the dustbin & just went on topping up.
The liquid drained into the bucket & every few days I decanted it into plastic bottles/milk cartons. Absolutely no smell at all. I used one of the bottles the other day and after 6 months there is an 'earthy' smell but only noticeable if you actually put the bottle under your nose. At the end of the season just clear out the bin (yes, that smelt) and it's ready for this year. Still trying to work out the dilution, about 1 in 15 or 20 seems OK. Best of luck.