When I'm out walking in public, I hold my keyring in my right hand and flip the keys back and forth. it's actually just a disguised version of common autistic hand-flapping, but it looks like just an absent, lost-in-thought gesture.
But then I also rock back and forth on the toes and balls of my feet while waiting in cues, so there's no suppressing a determined stim - but it's less obvious than the hands-in-pockets, side-to-side Stevie Wonder swaying that I usually do.
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"I don't mean to sound bitter, cynical or cruel - but I am, so that's how it comes out." - Bill Hicks