Been doing it for a few weeks now. We just follow the sequence, well some of us. Bit of a pain in the morning when you load your van with 100+ parcels one way, and REX decides the parcels that are totally buried should be the first ones delivered.
It gets better as the mornings goes on but the start point always seems really random. Too many timed parcels tends to totally throw it, but the powers that be want this, so best to just try and work with it.