Growing in Coco Mulch?

Has anyone ever grown in cheap coco mulch? how big or small do the chunks have to be? Do I mix with Perlite 50/50 ? Is Cal Mag a must or can I get away with epsome salts? in general, what is the watering cycle? it seems to retain water very, very well. To the point I'm a little concerned. Anyone tried this? I have to get this right before I shove 25 plants in it. I'm trying a 3x3 flood table sog in 2 gal grow bags with it. can I use river gravel for the base under the plants? I don't have access to anything to grow in so I'm using what I have around. I have to figure out how to use this because I bought so much of it. Any input is greatly appreciated as I cannot find much to read on the subject. I've had one guy tell me it works really well and sounds optimistic that it will perform. Just need a few details. THanks