As said, never abruptly stop any of these meds. Xanax is less addictive than valium and so it could be used to wean off valium.
To get off any of the benzo types it's usually 10% reduction / week if you've been on high doses or for an extensive time, that still has to be tailored to you as an individual. It's better to wean off ONE slowly, at your own pace, rather than add another.