If compressed air doesn't work, then you'll need to clean the Xbox controller buttons with a cotton swab and rubbing alcohol. To clean sticky buttons on your Xbox controller: ...

Does your Xbox controller have sticky buttons or bumpers? You can try WD-40 Specialist Contact Cleaner before you get your tool kit out.

The ability to decide which buttons do what on your controller should always be entirely up to you, so Microsoft has made sure you remap them however you'd like.