I have not had any blowouts with segments and have done quite a few. I do turn it at high speed. And if it is wood that I know that is easy to blow out, I stop and soak with thin CA often, turn a little off, and soak some more.
On the metal part, I use a modified scraper (scraper than is not square at the end but slightly angled across) and I keep my sharpener close by. I do not hesitate to spend about 5 to 10 minutes sharpening and honing it and testing to see if it matches my expectations before beginning a segment. I look at the scraper edge under a magnifying glass too. The point is that I don't attempt it until I have prepared the scraper for that specific job.
Then I take minute' amounts off. My goal is not the last 1/8 inch but .2 to .4 mm at a time. Then hone the chisel, repeat. I also do this over one segment joint at a time, not the whole pen. After reducing one segment about 1 or 2 mm, I hone and move to another segment and do it. I use calipers to see how close I am getting to the final size. And then I turn the rest of the pen to match the segment joints. Usually, when I am within .5 to 1 mm of final size on the segmented joints, I will start doing the whole blank from end to end
As you can tell, this will take a longer time, but the results are worth it. Others, I am sure will probably do it differently, but this has been my method.
Added in: I use the TBC and also used Epoxy or rubberized epoxy or CA. If I have time to set the segments the day before, I use use gorilla glue because it will fill all the space. Lots of time sections that do not have glue completely filled will let go. Most blowouts that I have had, I could tell there were voids / air space between the tube and blank where the blowout occurred.
Like you, on delicate blanks, I have sanded down rather than risk blowouts. It does take time to do it that way! On my favorite pen
seen here and the blank make up
seen here - do not allow for sanding, because sanding will cause the solder to smear terribly. The finished pen had NO sanding on the blank, only on the CA finish. It was turned down smooth using the chisel that I described above.