Another not-quite-sharp trick: ice. Look for an ice cube tray that makes crisp edges and corners. You can also freeze a thin layer of ice in a pan and break it into shards. Normal ice will not actually cut you but can feel like it will. (Extremely cold ice or big jagged chunks can cut, though.) Also if you move the edge or point in a cutting motion it can't frostnip your skin because it doesn't stay in one place. If you're squeezing ice in your fists, stop after your skin starts to turn numb.
Re: STIM
Another not-quite-sharp trick: ice. Look for an ice cube tray that makes crisp edges and corners. You can also freeze a thin layer of ice in a pan and break it into shards. Normal ice will not actually cut you but can feel like it will. (Extremely cold ice or big jagged chunks can cut, though.) Also if you move the edge or point in a cutting motion it can't frostnip your skin because it doesn't stay in one place. If you're squeezing ice in your fists, stop after your skin starts to turn numb.