I have used nair on my arms before and I think I would prefer to just shave them as nair makes hair come of in clumps and sometimes you have to scrub it off. You have to be really careful not to miss patches. It is a myth that hair will grow back darker or coarser. The hair will prickly for a couple of weeks until it grows back out.
I have used it to remove some hair on my chest and I put it on and let it sit there for 15+ minutes then had to scrub like hell and then had to reapply for another treatment plus the smell was horrible. But it did come off but it grew back just as fast as shaving for me.