Corral manure is much different than the separator manure we have to deal with, our manure pad is all manure from the separator and holding cells. The last 7 years we have used loaders to pile, dry and pile again, very expensive and inefficient. We have 4 980c Cats, 8 yard machines, they drink the fuel 7-8GPH (3406cat). I would hate to know what a grinder burns for fuel. We have been very careful on changing this system to more production and efficiency, one guy can just about handle all of it. The compost turner burns about 3-3.5GPH (3306 Cat) and is the least ran machine. The screen burns 1.5GPH (74hp Duetz) run all day costs hardly anything. We can feed the screen with one of our 3 yard machines 621 Case or 930 Cat 3-3.5GPH(5.9 cummins or 3304cat). I really don't think anyone can touch us on cost for what and how much we handle.
RDO has a 25000 cow dairy close to were we are and they do everything we do except that everything is much larger and newer. They spent half a million on a screen and about the same on a turner, I have seen their screen and is scared the crap out of me. They use the screen because they are using the manure for their 20000+ acres of farm ground and they hate rocks. The screen also works well for all the trash, leg and ear tags, string and any other trash the flush system picks up.
I think what your doing works pretty well for the drier corral manure, with our flush system we don't have much in the corrals. As far as a favorite shovel for digging out, I use the 3 strike rule. If I have do dig anything out more than 3 times it can go on the weeds.