To drain my barrels I just unplug the feed line at the pipe and turn on the
pump. I will sometimes just put the smaller tubing inside of a hose and water the yard with the old nutes (gravity fed). Works great, just listen for when it starts sucking air and turn it off right away or catch it just before then the barrel will only have an inch or so of nutes in it and you can easily pick it up and clean it out. I usually cut about a 18"x18" square'ish hole in the side of the barrel so I can reach inside to make adjustment, clean or add frozen OJ or water jugs to help keep the nutes cool in hot weather.
I found some picts of the tomato yo yo thing. Lots of places carry them!