You'll find the same guide everywhere you look, listing song titles and their location; it's perfect.
I wasted way more time than I had to just waiting for a song to change. Just skip and warp to the next location. Go down your list and try to make a route. I'd also try quitting to menu and resuming, and I definitely tried to remember to remove all songs from the playlist, for whatever that's worth. If the cops were after me I'd just reload checkpoint.
I didn't start profiling people until after the campaign and was running around trying to finish all the sides. After that, and going to all the stores, I was left with two: Blvck And White and Dark Steering.
I immediately followed online advice and went to the baseball stadium in Parker Square. I kept running around checking everyone and also across the street just in case, and almost immediately found one I was missing. I figured there was no way I'd find the second one there too so I tried the Navy Pier but wasn't feeling it, so I went back to the stadium and got my last one pretty quickly.
I say try pairing this with the online Public races, good idea to throw on the search and have that running endlessly while you run around town (though you can't use fast travel with an active search, so you'll have to exit and restart that if you do).