Assembly a custom mini-B USB connector
If you have to use that, a skilled technician with the wrong tools.  Needle-nose pliers would be the first and least ideal resort.  Something involving a block of metal with a hole drilled in it and then slit in two and mounted in a vice might be better, but harder to design.  Or perhaps take jaws for some other similar style of crimper, anneal them and modify.

But the better answer is to avoid hand assembly of such connectors if there is any means at all to do so - it is quite hard to get right, and there's a high risk of the wires coming un-soldered or shorting together inside.  

You would generally be better off purchasing manufactured cables with molded on ends and cutting the other end off, or see about having them custom manufactured in a facility that can fill them with some kind of plastic or potting compound.