Swimming is a natural and best way for Jal Neeti.
Traditional Indian method describe use of a specially made copper pot with a long snout and water kept overnight and then in particular position, put water from one side of nose, which comes out from other nostrils.
Few persons especially among Muslim populations use water in their palm and try to sniff it.
I advise it to do with 50 ml syringe. Boil and cool the tap water. In a glass of water, put 2 tsp of common baking soda available at home and a half teaspoon of common salt. then direct the water with help of syringe into the nose and ask the person to say ke...k.. k..k..k..k ... not stop just like indian kabbadi game. This helps to close the soft palate and water does not spill into throat. This technique has advantage that it gives a jet of water which washes debris effectively.