The key is to sand the area with the hole until you cut through the outer skin. When the area to be glued looks "flat black" then it's done right. If you just scuff up the area without cutting through to the underlying rubber it won't work. It really is obvious once you see it happen but it takes a bit of work to get it there.

Apply glue, wait until it's dull and you can't smell any noticable solvent and then patch.