practice on monsters.
its about timing. i think optimum time is just before scim hits, so you still get that scim hit but your 2h is out for a quick next hit,
if your too late its too slow
if your too early you change to 2h and just stand there.
it is alot easier if your opponent is equal or lower lvl so you can 1 click them.
2 clicking is a bit slower. also a quick comp helps
Edit - also you might want to get this moved to rs general, its not cheating and you'd get more help there.