lIKE THE comment above me said, kanye chopped his samples, create the melody with his chops and then ask his crew of musician to reproduce the new melody. There are people in the bussiness who are paid only to do this. so that's the answer for that, that almost none of us can do unless we got the $$$$
if not, EQ EQ EQ EQ EQ lol and EQ again. use Eq to take out what you hate, After use another EQ to raise a little bit what you like from what you have left. And last but not last EQ again what you hate, because raising frequencies certain places will raise the whole spectrum. So you have to re clean it again.
You probably won't believe me, but in this song produced by me, I use two samples. One fro the guitar/main melody and another for the vocals. And the part you probably won't believe, is that the vocal were not accapellas, I cleaned the sample with EQ. EQ is your best friend when it comes to sampling.
https://soundcloud.com/alwaysskilled/beats-by-as-on-the-run
or in this one, where i used one sample, and i chopped it, Laid my same chops on 4 different FPC on fl studio. One for my low, one for my mid, one for my hi and one for my vocals. then I played with them chops.
https://soundcloud.com/alwaysskilled/as-now-i-see
hope it kind of helps you create a vision on how to clean samples.