My experience with smoking crack is very limited as I never much got anything out of it since the two times I have tried smoking, I had already been shooting coke for hours.
However, I know that with IV coke, there's usually a nice hour or two (depending on the length of the binge) where you'll feel pretty tweaked out and shitty, lying awake and smelling that wonderful coke seep out your pours. However, if you've just taken one or two hits/shots (a mighty feat btw..) you can probably level out after thirty minutes or so and go to sleep.
As for benzo's, I've found that they help somewhat with the crash, but you got to be carefull not to overdo it. IME, drugs like Xanax or clonazepam usually take a while longer to kick in or make a dent in cocaine induced stimulation than they would if you were to take them without having used stimulants before hand. The way I usually would do it was to wait about 1/2 an hour after my last shot of cocaine, and then take my normal dose of Xanax (which if I was intolerant to, would be .5-1mg). I'd then feel reliefe within about twenty minutes and be able to fall asleep.
Also, weed does work for some, but for others (like myself), it's truly a horrifying tool to use when coming off of cocaine or any other stimulant, as it can increase paranoia.