None of the Windfinders, Wise Ones, Ashaman, Damane or Forsaken actually gesture or move their limbs when they channel.

The explanation we received in the book was that Aes Sedai learned how to weave incorporating those hand motions, and because this is how they learned, they developed blocks in which they need the hand motions to successfully trigger certain effects.

Rand doesn't have this block and doesn't move his hands while channeling most effects. It's possible that LTT had this block for certain but not all weaves, since he needed this aid to concentration for one of the weaves he used during the fight at the manor, but he's never noted the necessity for any other weave. He generally focuses balefire using his hands, though, but never mentioned that he needed to do it.

At the Cleansing, even though Graendal was hiding her ability and channeling, she didn't invert the first weave she tried to use, and that is what Verin reacted to - not any gesure or etc. We are told that Verin tried to Shield Graendal, the Shield wasn't strong enough, and then Graendal calmly turned around and started walking towards them while channeling attacks, the first of which Verin couldn't identify. Graendal wasn't gesturing or using any hand motion.