Knife???? Really! I hadn't heard of that kind of retouching. Wow that is a risk! Well, I would certainly make a dupe neg before attempting that Imagine you get a few minutes with some famous film starlet and then you take a knife to the neg...

Looking at that image in the link I pasted in, there are two quick giveaways of red sensitization. (1) The shadows are deeper in the red-sensitized film. Note that in many of Hurrell's images you have dramatic, deep shadows; this is actually hard to do with ortho film. I've found that the UV sensitivity actually tends to create the appearance of more fill and gives a less graphical, uh, Rembrandty look. Even with very directional light, ortho film gives quite a lot of fill. Also (2) there are of course many more blemishes in ortho shots.

Anyway my guess is that Hurrell started using red sensitized film he suddenly had a lot less work to do, to get the look that he wanted. Pure speculation on my part, of course.