Benzos are really the only thing that will totally knock out a stim comedown in its tracks. I've heard anti psychotics like seroquel do as well but I've never tried those. Opiates mask the symptoms for a few hours and you'll feel good for a little bit and then your back to square one once they wear off. I have been on adderall for months and have tried loads of prescription meds and otc meds to aid a comedown. Nothing works like a benzo because it actually sort of "fixes" the problem. Whatever you do don't smoke weed or take Benadryl! It helps for some but makes things WAY worse for most people on a stim comedown. If you can't get benzos or opiates make sure you eat a 1000 calorie meal, hydrate, and get a hot shower. That's really all you can do. Some other meds that may help ever so slightly would by hydroxyzine, valerian root, 5htp, l-tyrosine and maybe some melatonin. Keep in mind though that with otc stuff some stuff works great for others but makes stuff even worse for others, so use with caution. Like I said a benzo is really the only thing that will totally knock out a comedown.
Also, if you take a benzo or opiate please do research if your not familiar with them! And those substances should only be used for the more rougher comedowns, not every single time obviously.