The 50/50 STP and oil is kind of old school - like me LOL. The point, as stated above is to have something that will stick to the parts until you have a good oil flow. Also, as stated above, these days I'd just use any name brand assembly lube. You just spent how much on your rebuild; come up with a few more bucks to protect those parts during the first start.
Growing old is unavoidable. Growing up is optional.