I haven't done this in a while, but I used to manage without a vise. I'd line the two cone wrenches up and grab both through the spokes and tighten the cone with the other hand. I think that's what I did. It always took about 10 tries to get it right but that was part of the process. I still have those wheels 25 years later and they are fine but would need to be repacked if I wanted to use them.