[ChrisN]

I'm considering give it a go. I've watched a bunch of videos and read lots of informed text, but I've not seen an answer to something that's bugging me.

The tech will remove the strings and straighten the neck, then use the fret rocker, usually in 3 places on the fret (ends and middle), to find the "high" part(s) of each fret.

So far, so good, but, if you check a following fret using the high part of a previous high fret as the reference point, don't you necessarily get an inaccurate result as to the health of the following fret?

Also, I understand you check 3 frets starting at either end, find your high spot(s) on the 2d fret from the end, then move down 1 fret, but doesn't that method assume your starting fret was perfectly level? Or doesn't it matter if your start point is off because you're going to make the rest level relative to each other? If so, isn't that first fret likely to have a buzz if it's left high? In other words, I suppose, how do you rocker-test the starting/ending frets?