Bhop was patched in 2010 with the orange box update ABH is the remaining method. Firstly, you need a way to jump super quickly, you can do this with an AHK script [wiki.sourceruns.org] or you can use some custom binds by typing "bind mhwheelup +jump;

ABH is the ability to jump backwards and gain incredible, unnatural speed. Hl2 and Eps, Portal 1 - NOT Portal 2, L4Ds, TF2 or Counter-Strikes Gmod has been patched.

If you want to do accelerated back hopping on a game like Portal or Half Life 2, press the escape key when you're in the game and select options. Next, click on keyboard and select the movement called "jump." Return to the game, then hold do