After 2,1 f2 the only way to connect nut punch is with a f3 cancelled into nut punch. Make sure you get the full dash before pressing f3 xx nut punch. It takes practice but it is pretty simple.
And don't let people convince you that there is a better option, Cage gets at least 6% free damage off of chip damage plus meter whenever a nut punch is landed. Which usually is greater than or equal to the net damage you would have received from other combos.