And too, it depends on how much rust is on the thread and thread box. I hand brushed a 4.5" vise and it was good, but I got a 4" that was rusted up a bunch. Disasembled it, Hand wire brushed it to get the big stuff off, electrolysis for a couple of days, abother once over with a brush, linaeed oiled, and greased the threads, worked like new.
Just depends on what shape it's in and what end results YOU want. You can do a mix of what Bigred and I said; or read through the forums and find a process that fits what you want, with the tools you have.
It's all a learning process, so just have fun with it.