One of my favorite Dj's is 3LAU. He does these monthly mixes that sound awesome. It sounds like one big song.
Heres an example http://soundcloud.com/3lau/3lau-haus-22-march-mayhem?in=3lau/sets/3lau-haus
(I'm not sure how to link it)
I'm hoping someone can tell me what he does. Everywhere I look about finishing mixes they basically all have the same gist: All the songs are already done so you don't have to do much or even anything.

I don't believe that 3LAU has to do something to his mixes. He made a Tove Lo song that sounded like crap, sound like it was made yesterday. Can anyone tell me or guess how he gets his awesome finished sound on his mixes.