to sleep i recomend benzos for the most part. however, mixing benzos with another (hypnotic)drug or using another drug or drug mix may suit you better. heres some ways i get to sleep after amphetamine use:
mixing certain benzos to get a "full" effect- mix a hypnotic benzo(temazepam, flurazepam, triazolam, flunitrazepam, nitrazepam) with a benzo with strong anti-anxiety effects(clonazepam, alprazolam, diazepam) to achieve a "super-benzo" effect. also, one of the benzos should have a long duration(to keep you asleep) and one should have good muscle relaxant effects(calm restlessness and boosts relaxation).
mix a hypnotic "z-drug" with a long duration anxiety killing benzo- ambien, lunesta, etc. to induce sleep and either clonazepam or diazepam to ease anxiety and keep you asleep.
seroquel with a benzo- the seroquel knocks you out hard, but can have unpleasant side effects(restlessness, dysphoria). take a benzo with a long duration, good muscle relaxant effects, and strong anti-anxiety effects(my choice is clonazepam, but diazepam also works well). the benzo will offset seroquel's side effects and help keep you asleep(note you don't need that large of a dose of the benzo).
benzo with alcohol- good if the benzo is strong and lasts long. also the amount of alcohol should be kept low but enough to help you sleep. note that hangover effects are quite possible the next day.
benzo with sedative antihistamine- use a strong benzo with either doxylamine(Nyquil, Unisom; most sedating antihistamine, studies have shown it to have stronger hypnotic effects than phenobarbital) or diphenhydramine(Benedryl; strong hypnotic effects). because these antihistamine have unpleasant anticholinergic side effects, a benzo will ease them as well as ensure sleep.
opiates- works if theres no benzos. use a stronger opiate than codeine like oxycodone, morphine, hydrocodone. opiates generally aren't very good for sleep esp. on amphetamine comedowns, so some booze or a sedative antihistamine should help induce sleep.
alcohol- if you don't have any better downers, alcohol will get the job done. i recomend taking a couple unisom or benedryl to help put you out. with booze, drink enough that will get you to sleep and know that it likely will be "bad" sleep with a hangover and grogginess apon waking up.
*out of all of the above, the seroquel with a benzo combo is the one that will ensure sleep(seroquel puts you out with force).
