When I used to have meltdowns (before I went on antidepressants), I shouted profanity, hit myself in the face, stomped around, slammed doors, and, most of all, cried. What calmed me down was if somebody cuddled me, talked to me, and tried to get me to rationalize why I was feeling so frustrated at the time. I couldn't speak for a while after a meltdown, because I cried so much, but after catching my breath again, I could finally rationalize my thoughts. Unfortunately the meltdowns upset everyone else in the house, which basically prolonged the meltdown because I would feel guilty and angry with myself for making my loved ones upset, hence the reason I went on antidepressants.
But, how I calmed after a meltdown is not really that typical among Aspies, because most Aspies prefer to be alone to calm down, stimming in a dark and quiet haven, while I needed social comfort to calm myself down.
But I hope that has given you some idea for your story anyway. Good luck with your story. 
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Female