Depends on the match. In 1999 or 2000 I think, Fujita had a huge chance to beat Kimo in a New Japan worked shoot but Hattori (ref) DQ'ed him for kneeing Kimo down there while trapping and bashing him in the corner.
People who can hide low blows are Tenryu, Fuyuki and to some extent Gedo and Jado. When you're grabbed from behind, it's easy to fake flailing your legs so as to give the impression you're trying to free yourself and "accidentally" hit his nuts with your thighs. That's what these guys do.