You can't use a rod and nuts with horizontal dropouts. The key isn't whether they meet in the middle, but whether the faces are parallel, and a rod can't tell you that. The expensive tool, has large cups that you line up and look to see if the gap between is the same width all the way around.

I'd either pass on this step, or pay a shop a few bucks to do it right. That will be way less expensive than the tool.