Personnaly, I just grow them in the field. I do pick deep rich soil for them as they are heavy feeders. While they like nitrogen, they are nowhere near as demanding as corn. Good tilch ( which includes organic matter) and balanced nutrients are really all that are necessary unless you are trying for specimin plants or state records. It is wise to rotate them as they will deplete the soil unless you periodically amend.
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Nice cabbages. Boy would my birds like to have those greens about now (I realize this was taken previously). We have knee deep snow on the ground now. Nothing green to be seen except for pines and other evergreens.

I don't think the fertilizer requirements of brassicas are going to be consistent across the group, because there are so many forms. Some are leafy greens that need a lot of N, but there are root crops, those grown for flower buds, those grown for the stems, so it will vary.

Brassica soil is clay. In regard to organic matter, I beg to differ with my hero farmerdilla. Brassicas don't form mychorrizal associations, and they seem, in my experience, to not differentiate between proper garden soil and new, unimproved soil that is well fertilized (chemically). This has to do, possibly, with their origin as a seaside mediterranean plant, growing in soils that were poor in organic matter. Chard and beets (different species) share the same seaside origin, and they too do not form associations.

Fertilizer needs (nitrogen needs really) are approximately proportional to leaf area. They are lower for arugula or turnip, and larger for cabbage and collard. They also like soil on the alkaline side, or at least not the regular acid we have here.

I just don't find brassicas to be that picky. I have grown them in red clay, muck soil, sasafras soil, and currently in sand. Certainly they can be grown hydroponnically, but tilth is directly related to organic matter in the soil. Clay with out organic matter is brick, nearly impervious to roots or water. Sand on the other hand can't hold water or anything else. I am not going to the elaborate construction of raised beds and the importation of truckloads of organic material. I do plow down both crop debris and green manure crops to keep good tilth. While they prefer a near neutral pH, I have grown good cabbages at 5.5.

Here is a link that might be useful: brassicas grown in the last 5 years