"IN_ALT1 & IN_ALT2"
I'd say these are the left and the right ALT keys. Combining them with "&" actually lets you check if both are pressed at the same time. Not sure if that is actually useful in this situation, but maybe you can think of good combination.
No clue, what this BULLRUSH thing is. I've been wondering about it before.
Personally, I had my voicechat on left ALT for quite some time until I found that I get undesired behaviour, if I use the voicechat and look at the scoreboard at the same time (ALT+TAB.. yeah, cool hotkey there, windows), so I moved my voicechat to MOUSE3. This has another disadvantage: I can't talk and shoot at the same time.
Maybe you could create a pair of +command/-command and let the player decide where to bind it.
Or just hook on IN_USE by default, unless the player disables it with a say command à la
https://wiki.alliedmods.net/Commands...oking_Commands