Brewhouse efficiency depends on two things, your mash efficiency and how much wort you leave behind when transferring it to the fermenter with each step leaving a little bit counting. To increase the mash efficiency, you mill finer...uh, until you find that you can't drain the tun. OK, you do soon come to a dead end there.....or do you. I mill my grains until they look like cornmeal with the husks ripped to shreds. That gets me great efficiency but I'd never be able to use a manifold or bazooka screen. Instead I use something else to filter the grains out of the wort, a fine mesh bag. You can get one made from nylon or polyester. When time comes to drain the tun, open the valve. If the wort stops flowing out before the tun is drained, lift the bag. That bag forms a huge filter area so it doesn't clog. No stuck sparges, not even with wheat or rye. With that I can get a brewhouse efficiency of 85% EVERY TIME!