Your water temperature should always be at the same temperature.
Always use the same amount of water.
Make sure to weigh out your quantities of kava and not rely on a measuring cup. Different batches of kava will have a different consistency, some powders are denser, and some are more fluffy.
Invest in a blender with excellent power and a timer, so you don't have to wonder if it is blended enough before straining. It is not the authentic way of preparing but will save you time and money in the long run. You will be using less time, energy, and less kava to get the same result.