In my 17.5 Destiny car the only time I use my push brake is if there is a tight °180 at the end of the straight or some similar corner. As for drag brake I have 4% on my hobbywing esc. I am now running a locked axle setup and have not changed any of the esc settings yet.
Now for setup it will depend on the chassis and option parts you are running. Best I can suggest is to find a setup sheet that corresponds to your track conditions and car that was made by "one of the fast guys". Or post what your current equipment and setup are and I'm sure you will get plenty of feedback here.

Edit: I also have the push brake turned WAY down on my radio. I don't have an actual number currently since I am at work.