On this, Em keeps his vocal tone fairly low and at a consistent level, almost 'dullened' so it doesn't take much breath. So it all just becomes about delivery and timing. The flow of this verse is badass.
Anyway, having just re-listened to it; even without using punches, I don't think it's that hard to rap; as, I've noticed the key to it like many of Em's structured flows is bursts of rhythm. It's not one continuous flow, you can hear the breaks, it's bursts of controlled rhythms.
So, if you just relax and learn the rhythm (s)/ timing of each little segment (segments of bars), rather than trying to just spit every word in a fast burst, that's the key.