there is no timing, they are not deadly raves.
I learned these originally by watching my friends at the cades..
anyone can do them, just tap it out
you dont have to wait between hits, if you have seen remu's old geocities site then you can link them into infinites.
you can also edit your own stuff into them, which makes them flexible. Because of this people like me and charles prefer 3 to 4, even though 3 is plagued with infinites.