Best way to cleanly cut brownies?
I can't select either of the above answers as the best answer for the following reason:

The brownie I'm making is meant to be "gooey", and even after cooling for 2 hours, and then chilling in the fridge for another 30 minutes, the the upper-half brownie still remained fudge-like. I ended up using Jay's suggestion to eye-ball a 4x4 grid, however I didn't use a hot knife. I used a plastic knife with an up-and-down sawing motion and got fantastic results.  The cuts were as clean as you could ask for, and the entire process didn't take more than 5-10 minutes. 

As an aside: I decided to forgo the "aluminum foil sling" and just spray the 9"x13" pan with PAM, line the bottom with parchment paper, and spray it down one more time. The brownie "loaf" came out with zero fuss and had a perfect looking crust.

edit: I plan on experimenting with 2 large metal rulers to score the loaf, instead of eyeballing the grid.