thinning shears does NOTHING to reduce hair at the scalp, they only remove some bulk but they are only used mid shaft....not at the base.
the only way to really lessen density is to remove as JRob said, its time consuming at best. if its just a bit too dense , it will thin out a bit on its own with some wear and few washings.
you other option is to have the factory reduce the density.
DebbieS.