I was just doing a COMFREY short research on the net myself (lots there btw).
I have the regular comfrey, and will have more when I get a dedicated new space worked. I have been harvesting the leaves, putting in an empty plastic 'flat tray', leave out to dry. I am cutting off some stalks, then cut off leaves, put stalks/stems in trash. Rather than cut whole plant down, being selective.
The leaves have good N-P-K, especially the potassium, plus calcium and other trace minerals. It can be added to your compost or leaves used as green manure around plants. I am looking to add the crumbled dry leaves around plants, working in the dirt. The potassium is to good one for blooms/fruit, so a real benefit for tomatoes. peppers etc. As I do mostly herbs, and don't want much flower will be using more in flower bed. I am hoping to get some and bag (in brown kraft lunch bags) to sell at the market. The tea sounds nasty, and one more thing I really don't want to mess with!
Hope this helps