If i were to run some fine sandpaper over the discs to give them a bit of a clean/rough up would it help braking performance or is this a big no-no? i'm sure you can do it to pads with no problem?
Sand pads in a figure 8 pattern across some fairly course sandpaper. Rotors can be sanded with some finer (600 grit) sandpaper. Clean both with denatured alcohol after you're done.