I open mine about 1/4 the way for the first quart or two until there's no more chunks coming out, and then slowly open the valve all the way. By slowly, I mean over the course of about 60 seconds. Works for me. The only time I might have an issue is with a lot of rye, oats, or corn, which are all pretty dang sticky. I don't recall a stuck runoff with wheat although it's been a while. Gravity or efficiency will not be impacted in the slightest. The main reason to start opening the valve slow is to prevent immediate compaction of the grain bed and stuck runoff. By opening it slowly, the grain bed will not compact quite so much (at least in theory) and prevent stuck runoff which is kind of a PITA but not the end of the universe either. Like DarkSide said, you can always stir and start over, and add rice hulls if you have them and need them, which in my experience is a very rare need.