Haven't read the entire thread, so this may be redundant, and some of this may seem to be a keen grasp of the obvious, but I'm slow, so I beg your patience.
Removing material from a blank is a very violent act, even with a scary sharp tool. The harder the material, the more violence required, and the more brittle the material, the more likely that violent removal will have unintended consequences. So the first thing to realize is that the most dangerous parts of a blank are the ends. While removing stock, the middle has the support of the surrounding material. The ends do not. Most woods are very forgiving about this. Hard, brittle materials are not.
Purists may rightly take issue with some of this, but snake blanks are expensive and hopelessly cool, and my time is valuable, so I have developed an aggressive, zero blow-outs process for getting snakes done quickly:
First, I trim the blank along the flattest side, to get one perfectly flat side. Then, I have a jig that allows me to mount the blank, bushings and all, aligning the blank along the centerline of the tube, regardless of far off from 90 degrees any side of the casting was. Using the mic head on my saw, I set the trimming distance (with the jig I only have to do this once, because the centerline of the tube is the referent) and knock each side down, pretty close to the bushings. Takes five minutes to do this, and I will have removed most of the material one would normally remove on the lathe with a chisel.
Then, on the lathe, I use a heavy (40 grit) belt sander paper to round off the hard edges, and I knock them down quite far. Any hard, square edge on a piece of brittle material is, like the tube ends, dangerous territory. Go in even a little too deep with a chisel and you could break off more material than you intended.
Then, the chisels. I have a small Sorby gouge that works fine for me (the best turners here have recommend mastering the skew, and I am learning it, but for now, I use the gouge.) In removing stock, I start with the most dangerous part first, while the chisel is sharpest (and of course, resharpen periodically). I go at the edges from a 45 degree angle to the centerline, (not directly from the side) so that there is some support on both sides of the cut, until I get perfect roundness at the edges. Then I'll work from either side toward the center of the bank, decreasing the angle until I'm finally coming at it from 90 degrees to the blank.
Normally, I would say the purists are absolutely right; in all but a few cases, using sandpaper to remove a lot of stock is a bad idea. For one thing, it's a cheat, and it ruins the point and the fun of the lathe. For another, if your blank isn't round, the sand paper won't fix that. The objective referent for roundness is the edge of a chisel supported by the tool rest. However, in the case of snake blanks (and also Micapearls,) I am not above using 50 grit Gator paper to remove stock, though I usually do this only when I hear that sound (you all know it, I'd guess) that means I got a bit too aggressive and put a nice ring of pits around the blank. But get back to the chisel as soon as that's been smoothed over. And of course, keep checking for air bubbles as you go, and fill them once they're exposed.
Hope this is helpful. It certainly works well for me.