Ref Post #60, might you drill the holes oversize (say 2-3mm) push a small amount resin putty, as opposed to liquid resin, to the back of the holes, let that set so that the hole is now "blind"?
Then carefully drill the correct size for the fixing bolt - not the overall fixing - in the middle of the now-set putty, coat the fixing with the resin, slide that into the hole in the brick so the fixing bolt goes through the hole in the putty gently, and then tighten the fixing bolt so that should push any excess resin out of the brick out on the exterior surface, and not into the wall cavity.
OTOH , I think this would work better and easier if you use the sort of fixing where you screw an external nut onto the exposed thread of the fixing stud (can't remember what that's called).
Does that give you any ideas?