Don't cut any leafs 2 weeks before harvest.
Cut the lower 1/3 of the plant in week 2.
Then in weeks 3 to 4 recut the lower 1/3 of the plant. You need to do a judgment call as to which week you want to do the trimming. It depends on a lot of factors. I'd say week 4 is best in most cases, however some strains grow aggressively.
After that you leave your plants the fuck alone and let them do their own thing.
If you trimmed correctly you won't have any lower branches. Just one top cola, or a cola with very minimal side branches on top.