To open it, your best bet is to get your tool into the case above one of the offending bumper buttons and gently twist the tool to 'pop' open the facia. The noises are unpleasant, ...

How to fix an Xbox controller's bumpers and buttons without cracking it open. The standard version of WD-40 is designed to be lubricant, and can leave a residue, by design, to help keep said ...