I about to go vacation for a few days and I was looking to see how much cornstarch it would take to make a large amount of oobleck, but I suck at math. I'm trying to use it to dump into a tub and when I'm done with my fun I'm going to dilute the hell outta it to drain it. I would highly appreciate any tips and info

While bulk corn starch is relatively inexpensive (we used to get ours from a restaurant supplier), you should try some in a mixing bowl before considering scaling it up for recreational purposes. (Insert witty comment about 'life choices').

Oobleck looks awesome on camera. But having had my hands and arms in hundreds of gallons of the stuff, playing in it never crossed my mind. But then, neither has masturbating with a pair of pliers, so maybe I'm being fussy.

Seriously though - go to the grocery store and get a large container of corn starch. Fill a bowl half way with water no warmer than room temperature and start mixing in the corn starch. You'll find out if it's something you want to play in and answer your proportion question at the same time.