I did 4 tracks of vocals, just recording straight through to the end. I actually exported a sub mix and recorded the vocals to Pro Tools in CCRMA Studio C. Then I exported those raw tracks and did some clean up editing and some plugin effects in Ardour.
For the first rap verse, I made a copy of the main verse track and ran that through an EQ and approximated a "telephone" eq, then ran that through the ADSR envelope and automated movement on some of the parameters to create a changing effect over the first few measures of the verse. Then I brought the original vocal (doubled via doing it twice) back into the mix and faded the effected vocal away. On the last line of that verse, I added in another track where I ran the main vocal through the "Barry's Satanic Maximizer" plugin, which is basically a meaty distortion.
For the first section of unnecessarily repeating "play me a beat"s, I left 3 tracks normal, and then took one and again, ran it through the telephone eq and ADSR, automating the ADSR motion in the same way, but unexpectedly, when I went to play back the automated take, while the settings were as expected, the plugin acted very weird and created a saucy distortion, which I ran with, and recorded that effected track to another track and panned it ear to ear, all the while leaving in the telephoned version. I left that telephoned track alone so that throughout the song there's a telephoned vocal track present.
For the second rap verse, I definitely recorded that sucker four times with slight variations and that's about it. Of course one of them is telephoned and I strategically cut at the end so that the last two guys that kept going after the beat stopped were on the Barry's track and the telephoned track.