For those using test kits requiring powder reagents (i.e. Hanna Phosphate checkers) - I have found a relatively simple way to improve the powder dosing...

Hold the packet diagonally so that one corner is at the bottom, tap it to make sure all the reagent is in the bottom corner, then using a pair of scissors, cut the packet entirely in half diagonally.

It's then very easy to "pinch" it into the shape of a spout making it easy to pour and visually confirm that all the powder had been added to the cuvette.