Yep. That was one of the main ways I fed my grow this year and just harvested several lbs of the best bud I've ever grown. I'd have to say kelp, alfalfa, and EWC is like a super food for MJ.
Yes, but you may want to wet the alfalfa/kelp for a couple days before hand. Those amendments can get pretty hot. OR, make a botanical tea: 1 cup total botanical meals - .5 cup if it's powdered 5 gallons water Bubble for 24-48 hours Drench soil, topdress with dregs.
Does it have to be contained in something or can they just go in the bucket, bubbled and then poured?
I tend to put my ewc in either painters cloth bags or silk screen and let the annendments float freely. The purpose for this is durring the brew process I like to literally steep the bag in the water and wring it out several times. Might be one those things filed under "unnessesary shit" but its just a part of my process. Then I give it a good stir while scooping out water so the solids make it in ever drentch.
Alfalfa is super hot. ITG advised me to mix some peat and alfalfa and set it aside, allowing to cook on its own. Then using that to top dress... When I top dress kelp I do my best to 'dust' the pot 360 degrees 4 in. out from the stalk, toss some EWC on there and you should be good to go.
I didn't bother to cook mine. Sometimes I made it into a tea first and a sometimes I just mixed it dry around the top of the soil. As long as you don't pile it around the stem it will be fine. It's when the hot amendments come in direct contact with the roots/stem that they can burn. I've used several "hot" amendments as top dressing with no I'll effects. If you were mixing a soil that would be different, and they would need to cook. But again, that's because the amendments are coming in contact with the roots. Hopefully one of the organic guru's will correct me if I'm wrong but this has been my experience.
After the transplant I top dressed with alfalfa meal. The soil I used was FFOF, and only added that as it was the only amendment not listed on the bag. Didn't really have time to cook my own soil, but my next grow will be my own BioD mix. The plant seems to be doing exceptionally well and doesn't show signs of stress.