In ghusl only once you make niyyat before starting is enough no need to repeat 3 times and no need to do niyyat before washing each part just do niyyat once before starting ghusl and washing each part under shower is ok. rule no 367 is saying , while standing under the water jerks each of these parts on one's body with an intention of performing tartibi ghusl,it will not be sufficient. but in your case u r turning your body so it is right way.