Can you? Cause Im on a really high ledge now but there is a railing there and I wanna throw him off, so is there a way to throw him over?

There's only a few places you can do it, which sucks. There are however some places that do allow it without the command on-screen. Just find somewhere and keep slamming A.

if you have snuck up behind and grabbed him, you can just move over to the railing and turn around so he is facing over the railing then pull R..
most of the time it will work and you will knee him over the edge.

unless you meant the hanging underneath and sprining up and grabbing him thing.
then.. i dont know, usually you can do it..
try whistling to bring him over.