From what my sifu has told me, Wong Fei Hung would do criss-crossing swipes at the eyes which would conceal his speedy kick coming from underneath. Nothing other than a visual trick combined with great skill and speed. The times I have seen my sifu re-enact what it allegedly looked like... it seemed to be a nutshot.
"If you and I agree all the time, then one of us is unnecessary."
It is impossible to defeat an ignorant man in argument.
- William G. McAdoo
Against stupidity, even the Gods contend in vain...