How briny should the water be when soaking broccoli to remove bugs?
Ah... I remember doing this growing up. Usually used a small handful of table salt in a sink full of water, and the worms would be floating on the top after about 5-10 minutes. 

Most of the worms.

Sorry I can't give you a more precise ratio; I actually suspect soaking in water does more good than the salt - the worms don't swim. 

At least, most of them don't.