It is the bark that has dried onto areas where the trunk died back in the past that is the trickiest part. It's worth taking time to avoid tool marks. That final layer, a thin skin of brown/red bark is difficult. A dremel with a wire wheel will take it off quickly but will leave tool marks. Small and hardly noticeable but still tool marks. I have found that you can peel down to the final layer easily. Get it as thin as possible without marking the wood then wait until you have a wet period, a few consecutive days of rain. If it's thin enough and exposed to moisture for long enough it can usually be scraped off with a semi dull blade or even fingernails.
Here's a bit I'm working on.
View attachment 117920View attachment 117922
This one below was all dead and dry bark on the right, left side came barkless. Cleaned this spring(mostly cleaned), no tool marks.
View attachment 117921
I've seen demo vids with people scraping and brushing away with wire brushes, wheels, etc to get it done quickly, makes me cringe.