OK, I know what burnishing is and what it does, but not clear on how to do it.

Do you do it fast, lots of pressure, or just the opposite?

I guess it depends on what you need to do. I usually work from both ends towards the middle which tends to pack the threads together. More and more I'm using a round steel rod which I keep clean and instead of just pushing the thing across the thread I tend to roll it under pressure along the thread. It just seems to work better for me and closes up any small gaps which I might have.

Work towards the middle from both ends. Just apply enough pressure to pack the threads. Too much pressure and you can scuff the thread. You can use a Bic Pen with a round body or any other smooth, realitively hard, round instrument.

I have used the back side (the non cutting edge) of a single edge razor blade. Inexpensive and we need to have them any way. It work pretty well and can double as a thread pick as well.