I've been using wire cutters and carefully grabbing the shaft right at the shoulder above where threads quit - yes, leaves a mark, no, its never caused a prob since seals never move across that part of the shaft. Built plenty that way.
If I have to pull a shock apart I'll use a fine file and remove that mark so it doesn't harm seals when I put it back together. Shafts are pretty hard and you don't leave that much of a mark anyway.