I found that some clones take and others don't. I've done this in soil, coco and DWC... every time the same thing. Some clones take and some don't. Maybe it was my attitude towards them, I don't know.
To answer your questions... personally I like to go straight to flower schedule, and I'd keep the ec/ppm's the same as I would growing any other way... which depends on strain. I usually start flowering nutes at around 1.0-1.2 ec. Peak at 1.8-2.0 ec (i haven't got my truncheon on me and I don't know conversions off by heart, although 2.0ec is 1400ppm).
Not sure on the size of the container you'd want to use. The size I used was 6litres per plant.