So here's a video from one of the chefs I worked for and still respect a lot to this day.
What is seen here is his nigiri technique using only rice (usually 13 grams, but no more than 18, most places I've worked at use a happy medium of 15 grams of rice.). He pushes his finger into the rice to create an air pocket, make the rice lighter, it will just break apart in your mouth perfectly, the next is shaping, which is done very lightly as to not over pack the rice.
Each day I worked there he'd have me make 20 or so with left over rice, he would insect each one, holding it up to sunlight to see if it was packed to tightly, picking it up with, fingers, chopsticks, and dipping it in soy sauce. He would tell me if I saw a customer who ate with their hands pack it light, if they use chopsticks, a little tighter, and if they dip it in soy sauce rice side down, pack it even tighter.
He had a really keen eye and cared about his customers and fellow chefs, it's amazing how much consideration goes into each piece he made.
I am still no where near his level, but I constantly practice his technique during slow times.
Here's a quote from him that kept me inspired when people would tell me I was doing something wrong: "Not Wrong way, different way, sometimes your way might be better, sometimes mine might be better, but not wrong way."