A: Welcome to the wonderful world of multitrack drumkit recording! Bleed into the hi-hat microphone is pretty much a given. About the only thing we’ve found that can remove bleed is to use highpass filtering, which will at least cut down on kick, snare, tom, bass guitar, etc. that may have found their way into the hi-hat mic. Since the hi-hat frequencies are so high, you can crank the highpass up fairly high without impacting the hats, which will reduce most bleed quite a bit.
But a bigger question is, how much do you really need the hi-hat mic? On most multitrack drumkit recordings, not only do you get bleed into the hi-hat mic, but the hats bleed into everything else, too. Try this: Mute the hi-hat mic/track. You can probably still pretty clearly hear the hats in your mix, from bleed into the other drum mics and particularly from bleed into the overheads. Now, unmute your heavily highpassed hi-hat track and raise its level just a touch — all you want is enough of the hi-hat track to give it equal presence with the other tracks; the majority of the hi-hat sound is coming from the other tracks. In some cases, you might also want to boost the highs on the hi-hat track so that you get even more attack and crispness from it.