-- paraphrasing here --
"How do we find ways to describe the exact motion of jerking a thumb in some direction or nodding in agreement?"
But we can step back and consider gestures in a wider sense.
The words that describe the movement of body parts depend on:
Whose POV are you in?
What emotion and meaning do the physical movements represent?
What reaction are you trying to call from the reader?
(My first advice is to get hold of some Dorothy Dunnet and watch her characters do gestures and indicate things. She is just so good.)
Now, I have my WIP in front of me -- the Pax Manuscript. Let me look at some of the head/face/hand movements and try to figure out why I did them the way I did.
"Something stronger?" Galba nodded toward the upper shelf where a bottle of twenty-year-old brandy inserted itself into a row of books.
Simple straightforward nod. You get to do five or six nods in a manuscript. Don't beat yourself up about it.
Not everything has to be fancy.
(Never use nods to tag dialog. You're just wasting one of those five or six nods you're entitled to.)
Now 'motioned' is about as weak as you can get in the way of description.
Does she raise her hand up over her head and wave it back and forth? Does she make a beckoning with just her fingers?
We don't know.
But we don't have to know.
We can be vague for three reasons.
(a) The purpose and outcome of the gesture are crystal clear and straightforward and have no hidden depths.
The gesture doesn't mean more than 'come here'.
(b) We have a picture of what's going on. We 'see' her dust her hands of breadcrumbs. With that strong visual laid down, we can be vague about the beckoning part that comes next.
(c) Doesn't matter what the reader imagines that gesture to look like. We don't minutely describe it because it is inherently not important.
All that said, we don't use weak words like 'motioned', 'gestured', 'moved', 'pointed', 'indicated' and so on but two or three times each in any mansucript.
He'd left France with various English coins, handy for bribing. He fumbled one loose. Turned out to be a shilling.
He held it up. "There's two of these waiting for you at Number Seven, if I catch up with her." He
The boy's eyes shifted. "Down there." He pointed east. "She give me halfcrown to say she gone t'other way."
He flipped the shilling to the boy. Collect two more tonight."
All these motions with the coin, with the boy's eyes, with his pointing, convey complex intention. But this is one of those counter-intuitive cases where the gestures are filled with information, but the intention doesn't live in the details of the motion.
We don't have to describe the exact gesture of tucking the coin away. The meaning of that gesture stands there shouting. It doesn't need the support of visuals. It doesn't need the internals to spell out what's going on.
Sometimes, a gesture needs support.
If we say merely,
She thumbed at the air behind her in the direction of Codyville.
"We go that way."
the motion sticks out like ... well ... a sore thumb, and we keep wanting to say something exciting and specific about the thumb motion itself.
But the motion of the thumb is not important.
She clenched her teeth, making a sound midway between a dentist's drill and a pot boiling over. When she thumbed the air behind her in the direction of Codyville, it was if a particularly nasty ghost was following her and she had some hope of putting out its eye.
"We go that way," she said.
The second passage doesn't define the movement of the thumb any more clearly,
but we've added so much value to that motion in internals we don't have to add value to the simple physical act.
Thumbing toward something or jerking a chin in the direction of something you can maybe do twice in a manuscript.
After that your folks have to keep their chins and thumbs still and maybe just glance that way (2 times), indicate with a subtle lift of an eyebrow (once), roll their eyes toward (once), motion a languid hand in that direction (once), indicate with a hunch of the shoulder (once), nod toward (you have 5 or 6 nods, total), grimace at (once), twist to look at (once), notice over their left shoulder (once) ... well, you get the idea.
Another movement of hands:
She pressed her hands together in her lap, knuckle to knuckle, and waited.
Here, the motion and placement of the digits is important. We describe the exact location and placement of the hand because it is the visual that creates atmosphere for the reader. The visual itself becomes the comment.
Deliberately, she calmed her hands and set them together, loose in her lap. Her hands would whisper,
And here we have both detailed motion and internals. Here the reader doesn't need to interpret the meaning of the hand motion and placement. I tell her what it means. Belt and suspenders, as it were.