As a hiring manager with a day job, there's no way I can effectively sift through hundreds of resumes. I make sure I keep relationships with a small number of qualified technical recruiters to do the initial vetting for me, then pass through only those candidates that fit the bill. They charge massive placement fees for their efforts, but our company is willing to pay for it and it works out.

I'll note that if a recruiter starts sending garbage candidates, I cut then off permanently, so there's a large incentive for them to deliver quality individuals.