I used a plastic box I found at my local hardware store and it was crazy expensive, like $20, but this is Japan and it's expensive here. The ones I use for my mothers were $1 though. Some people make them out of used 2 liter coke bottles.
For that many plants I would recommend putting them all in their own buckets like the guys pic a few posts above. With that many plants it would be awesome if you could drain onto the floor like some people do and not have to worry about collecting it.
After I mix my nutes I first feed the base of every plant for a few seconds and then I try to cover all the surface area. I use one of these to make it easy on me, it cost a few bucks and is batter operated