What I do at the shop is tape off the blank that you don't intend to do anything with...put tape on both ends of the exsisting guide wraps. I use a fine file, but lightly file off the epoxy and take extreme care not to file away the fibers of the blank. All you really need to do is make the area smooth for your new thread wraps, so don't go overboard. All you need is smooth. As far as the build up of epoxy that is filling in the gap between the blank and where the guide bends I just take the edge of my xacto blade a pop off the epoxy.
After trying many different ways over the years, including the use of files (YIKES!), isopropyl alcohol, and acetone to remove the epoxy residue left after a guide was removed, I stumbled on a method last year that is so easy and simple I'm surprised I have never heard of it. What I stumbled on is using a wooden dowel of 1/8"-3/8" diameter to rub the epoxy. Just rub the dowel over the area the epoxy is on the blank after the guide(s) is(are) removed with a back and forth motion. As dumb as this sounds, you will see the epoxy being removed by the dowel as it gets heated up from the friction.
Like I said, it is so simple and straightforward it is amazing. The epoxy gets removed so well that there is no residue left at all. This means, if you don't measure where the guide was placed before you did the wooden dowel rubbing trick, you won't be able to tell where it was unless there is a nick in the blank's finish where the guide was mounted. And there are no chemicals, heat, or other things (like files) that can damage the blank.
The rounded edge. You will find the rounded edge develops an indention after doing a guide or two and that the indention actully speeds up the removal of the old epoxy and residue. Like I said, it is so simple I'm surprised I've never heard of it before.
I stumbled upon it when I couldn't the acetone and plastic scraper I had been using a few years ago. There was about 18" of 1/4" wooden dowel sitting there on the shelf, so I decided to use it to see if I could loosen some of the old epoxy and then take the rest off with my finger nail. To my surprise, I found rubbing the old epoxy and epoxy residue with the round side of the dowel removed it so easily and completely I couldn't believe it.