I'd contact print a step wedge for a predetermined exposure. But the measurement of speed for print material is done in a different way than negative films (for example, measures the exposure necessary to get midtone, not shadow) and I still recommend to review the ISO method and the idea behing it.
I was hoping there may be some sort of quick 'litmus test' I don't know about I could do to get an idea of the general speed range.
I'm determining exposure times by trial and error and if I could get a better idea of the true speed (probably around a 6 but I'm just guessing) I could control my exposures better.
I'll give you suggestion a try.