The Waterpik is more effective when you use the waterpik before brushing your teeth because you can use the waterpik to remove food debris and plaque from your teeth.
Then after you use the waterpik you can brush your teeth to have the cleanest teeth and you can use the Waterpik again after brushing your teeth if you want too.
But use the Waterpik first and then brush your teeth for the best results.
The Waterpik works great but I would also use string floss at least sometimes to keep your teeth really clean.