I dont ever just soak anything I feed. I sometimes "cook" things that I feed. Rolled corn, beat pulp. I do this by getting really hot water, pouring it over whatever I am "cooking" in one of those orange coolers and screwing the lid on and letting it sit for about 15 minutes. I always just eyeball it for how much water and squeeze some out. My reasons, and why I was told to do it yrs ago with beat pulp, is that "cooking" or basically steaming it like this brings out some of the natural sugars in the beat pulp making it more palatable for some calves, I think the same goes with the corn. I know some that "cook" their corn in a crock pot also. I also find that when its really cold the warmer feed makes them dig in a little better sometime.
You dont want to cook for a long time though, you dont want it to expand much before feeding, that would actually reverse the effect. To get more gain out of the barley they need to consume more barley, if it expands a lot from cooking, they are going to fill up on less and not get as much nutritional value. We feed the beat pulp, which is dried as I assume you know, in order to increase fill. The goal is for it to expand in their stomach and hold that fill while it breaks down, if it was already expanded a lot when you fed it you wouldnt get as much result. The cooking is actually more to increase palatability, so you want to cook it just enough to bring out the sugars and make it taste better to them, but not to the point of it expanding and decreasing their consumption. Thats why I just use hot water and the cooler.