I used to spin hip hop pretty much exclusively (although when I first got my turntables it was because of jungle and drum n bass), and honestly mixing hip hop is all about catching “that spot” in the track you are mixing out of and the track you are mixing into.
Golden age hip hop has a vast and deep catalog of memorable hooks, single verses, even just the stabs from the opener of a song can be memorable enough that you can tease with it but cutting it in on beat with the track you’re mixing out of, only to drop it with a slam and everyone will love it, even if the tempo is a somewhat significant change (watch any good DJ drop in Black Sheep’s The Choice Is Yours for examples of this).
DJ Premier convinced us all to rock doubles when possible, Qbert showed us that scratching is more than just that wikki-wikki noise, and honestly works well as a transitionary element in mixing. DJ Z-Trip and DJ P showed us that you can make anything hip hop as long as you give it attitude.
The skills that I worked on most when DJ’ing hip hop were back cue’ing (crossfader off, so it isn’t heard) as fast as possible, in order to bring a phrase back in on beat, transitioning between tracks that referenced each other via sample choices, using the same lyrics (mixing a track that samples the chorus of the track you’re mixing out of, that sort of thing), using horns, sirens, other loud elements in a track as stabs across the last 16 of the track I was mixing out of, and when playing more commercial/top-40 hip hop, just trying to find something put out by Top Secret or Satanic Mashups so I didn’t have to play the same damn version that was already all over the radio, or at the very least, using a re-edit/remix/mashup version to mix in and out of a current pop/chart track.
Getting to know the classics in hip hop will allow you to know when a current track references an old track, and might give you ideas on little sound bites to use that will make your mixing resonate with the audience. They may not know WHY they are suddenly nodding their heads, but when you drop the beat, they’ll get out and dance, because they’ve been drawn in by cultural memory.
A lot of hip hop from the late 90s and earlier is going to be out of key because of the way tracks were built from samples recorded at higher speeds and pitched down or adjusted in less-than=a-semitone of pitch simply to fit in, timewise, so trying to mix in key with old hip hop is really, really hard, and can be so hard that it becomes pointless.
Since you say you’re using the S4, I’d recommend that you take advantage of the sample decks and go through your collection of hip hop and grab loopable pieces that can connect up between tracks, whether its mostly lyrical, mostly drums, a bassline, a bit of a hook, whatever, just those classic elements that scream hip hop, and also, go and listen to other hip hop dj’s. Whether its mixes online, or mix CDs, or at your local clubs, pay attention to what you like and don’t like, and note it, and practice what you learn.
Hip hop is really hard to dj, and I don’t envy dj’s who can only spin top-40 and commercial hip hop at their nights because they really are losing out on so much of the really spirited, raw, gritty stuff that made hip hop so great.
Every once in a while you a really good commercial track that has that, Nas’s Hip Hop is Dead was full of classic stuff, you could tease into it or out of it with a ton of tracks, and I loved dropping the original Ray Charles track as the tease into Kayne’s Gold Digger as well.