The best method to avoid that nuisance of a mixture of hatched naupliae and unhatched eggs is to buy the best quality. In Germany it’s Sander’s. The hatching success is nearly 100%. But it is very expensive. One canister costs nearly one hundred Euros.
The second best method is the right tea sieve. I saw this when I was in Paris with Olivier Perrin. He sieves the hatched brine shrimp a second time with a sieve that has exactly the right wideness to let the animals through and holds the unhatched eggs back. Probably you need little experiment to find the right sieve.