im fairly new to jui-jitsu also. my gym luckily has a 10th planet coach. and like i said im new so i dont know how good my advice is but it works for me.
if my hand is gripped for the armbar for me its just about done with, however if i feel an armbar coming i clasp my hands together and get out of it 100% of the time.
or if your talking about sinking it in throw on a douchebag.
hope that helps