We screw treated lumber stringers to the wall. Gino will say that invites birds nests and wasps, but bird nests have never been a problem and I've been doing this for almost 30 years. Then you can attach the faces to the stringers with screws into the wood. Way easier to handle on a multipanel sign rather than having to drill into bricks while holding the sign. Plus, since the sign faces will need refurbishing/replacement in 5-10 years, it's a lot less trouble, since the stringers will last way longer than that. I also think the sign looks a lot better and more professional if it's not flat on the wall. In addition, the wood stringers will even out any unevenness in the surface coming from the masonry. When you put up the faces, it may seem most direct to start at one end and go to the other, but it's a better technigue to put the center one up first. Put your 4x8 as the center panel, prestart a screw in the exact center at the height of the top stringer, and screw it to the top stringer exactly in the center. The panel will balance while you level it and put the second screw in. Then once you've put all the screws in you add the end panels by butting them against the center panel and lining up the letters or images that cross the seam. Hot tip: before you letter the panels, check that the ends are actually cut square. They don't always come from the factory that way.