I know to tether is more of just tapping R1 but to grapple places sometimes it's fairly easy other times fairley difficult. Is the trick all in the timing? in the videos it looks so easy...

Hold on one target, let go on another. From what I can tell, you start off without that auto-aim grapple cursor. But I can't really tell when it comes in.

you start with the tether indicator. you can tether to anything as long as the spinning square thing appears in the aim reticule.  tether two things aim at something and press and hold L1/LB aim at something else and then release it. you can only have one tether out at a time. if you go to fire the tether again the previous tether will disappear and the object wont be together anymore.