Let's be sure of our terms here - I hope you mean 'vacuum to waste' and not vacuum to backwash. The former will bypass the filter, preventing the need to backwash - the latter will scr*w up the filter very quickly by putting the dirt on the wrong side of the filter media.

A time honored trick to vacuuming to 'me' () is to run the filter while brushing the pool, then, after an hour or 2, turn off the pump overnight. This will let the liberated debris settle into the usual 'low flow' spots in the pool where dirt usually accumulates, allowing you to vac to waste the majority of the debris in a short time, thereby loosing less water.

As Lisa said, get as much of the large debris out of there first!