c.a. glue and epoxy both work. i use c.a. rough sand the metal side, apply even coat of c.a. to entire surface, apply break pad. after positioning pad, i put a block of wood on top and clamp it for a few minutes, or just press down on the wood. this makes a nice flat fit. be sure not to glue the pad to the wood. metal can be stuck but is easily removes with knife.
after glue is dry, i trim the edges of the pad to clean up glueand then scuff the pad side by rubbing face down on a piece of 400 sand paper in a circular motion for a few seconds. this preps the pad for use and removes any glue.