After seeing a couple of posts on this, I figured I'd post a link to this page:
And here's another, same concept:
Yes, I know, it's not a Vulcan shock, but the principles are exactly the same. I did not have a syringe for inserting the new fluid so I used a straw (can't remember if it was a coffee stirrer or a wd-40 spray straw) and a container with a very small pouring lip (came with my iron). Worked beautifully.