What is one method or technique that if applied with enough frequency & intensity results in enlightenment?

Practice “not doing”.

Seriously, that’s it.

Bring awareness to what you’re doing without judgement and soon enough you’ll become Awareness itself.

In this context, “doing” includes thinking and feeling.

Clinging to thoughts is an action.

Reacting to thoughts is an action.

Judging is an action.

The actions of clinging, reacting and judging create identification with something other than what you are.

Stop doing this.

Practice not-doing, abide in Awareness, and enlightenment is certain.

Abiding as Awareness is not-doing.