Thanks! I've seen Mark showing how he oils a mainspring of a hand winded watch, but I have not seen any showing him doing it on an automatic. He then shows all of the oiling spots, goes through them one by one, but never shows or mentions what he does to the mainspring. If I am wrong about it then I will stand corrected.
Pre-oiling the mainspring, just like you do with the (lint-free) tissue paper, will cause, when the spring is wound with a mainspring winder, for the oil to spread up all the way to the place that should get no oil at all. There will be no way to prevent it.
This tends to be a personal preference thing.
With modern white metal UB mainsprings, theoretically they don't need lubrication. Most people however do, Mark himself does but just doesn't show it on every video. There is one or two where he demonstrates how he does it.
Personally I use a small piece of tissue paper to apply a thin smear of light grease rather than oil. Others fit the spring and apply 2 or 3 drops of oil which then spread through capillary action.