Squeegee.
I put 300 gallons of the stuff down at work last year with a guy who once ran a striping/sealing crew. He was an artist with the squeegee, made it look easy. Once you get a feel for pulling the stuff uniformly, you'll never look at a brush again. The 24" ones we used were like $32 at Home Despot.
Also, surface prep will make your life much easier. If nothing else hit it with a leaf blower. Rock and debris make the job harder and your finished product look crappy.