With a few console commands, it's not hard to do in half-life, but if you jump in CS you will lose all of your speed for about 3 seconds until you recover. And no matter what I do, I can't get it to work.
Spectating others who can do with it ease (lots of them in 35hp servers) only adds more questions because they do not lose all of their speed after a jump, and sometimes they can fly at over 1000 u/s with a parachute. They don't want to tell anyone their method, either.
Does anyone here how do they do this?