SO many different ways to treat a rap vocal, depends on the rapper, the tune, the tempo, the dynamics so many factors and variables to consider.
However I like to start with a gate and get the vocals nicely tightened up, then I’ll eq with a pultec EQP1a. For the bass end of the vocal I’ll boost at 60hz by 1 or 2 notches and then attenuate until I’m happy with the bass frequency response.
Then for the mids on a broad enough bandwidth say 6 or 7 I’ll boost either the 3K or 5K frequencies (depending on the vocalist) by 1 or 2 notches and attenuate the 10K region if needed (although I tend to like to leave that alone at this stage).
I’ll then compress using an LA2A with about 2 db of gain reduction to tame the peaky transients.
After that I’ll eq again also with another pultec to bring back in the frequencies compression might have muddied up usually boosting the 8K or 10 K by about 2 notches and then I’ll add another compressor, probably an 1176…this is where it gets fun…
If I want the vocal to really pump I’ll look for a fast attack and fast release on a 4:1 ratio reducing the gain anywhere from -2db to up to -8db to slam it. Then EQ again with a nice parametric EQ to get the final tone I want on the vocals.
To finish off I’ll often use a touch of tape delay, with a tiny bit of feedback as an aux timed at half the tempo of the track (kinda acting like a doubler), turn up the delay fader until you can hear the delay then back it off by 5db so it will be barely audible in the mix, but it does something that just makes the vocals pop out a bit more.
All that being said I have found myself with great rappers nearly not touching anything but the fader and a touch of EQ their delivery has been that good!
Maybe as @Dan_Pirate suggested post something you’re looking for advice on vocals wise in the “feedback category” so some producers can chime in with what they might do, which could give you some ideas to expand your options.