I have five rows of comfrey and two rows of nettles grown properly with weeding and hoeing. I am also using sweet cicely which also makes a good liquid fertilizer. I harvest them by cutting near to the base of the plant and take off all the leaves. They are then put into one of two very large butts I have. I do not add any water, although I have made comfrey tea using water in the past. I leave the comfrey, nettles and sweet cicely leaves in the butt for about a month or two. However, I keep draining off the tea using taps at the bottom of the butts and putting into the dustbins with charcoal.
The tea looks just like Tomorite to me.
Ken Thompson in his book "An Ear to the Ground" says that Russian Comfrey Symphytum x uplandicum is rich in all three main mineral nutrients, nitrogen, phosphorus and potassium but it is not unique in this. "Some plants can do just as well, maybe even a little better including: chickweed (Stellaria media), nettle (Urtica dioica), sweet cicely (Myrrhis ororata), fat hen (Chenopodium album), goose grass (Galium aparine), and hedge garlic (Alliaria petiolata). So I chuck some of these into the butts as well.