A lot of the checks can be done before start and before the Pax arrive. In corporate flying we have most things ready including the start up clearances before the PAX enter.
The idea is to start taxi and takeoff within minutes in one flowing move.
Its much easier with a Co as he can check what is done and that nothing has been missed.
Single Pilot in a light aircraft its often easier to do things from memory and then visually check against the check list to confirm.
A Military Pilot used to instruct by getting his students to the line up point without a checklist only then would he let them use a checklist?
Has to be better than flying by numbers as the time you will forget an item will be the time you cannot use the checklist for one reason or other.
Pace