Just do what my FC did; TEA time. We dedicated one day a week (I'd have liked to have done more days but time/work/life of other people) where 5-7 of us would go into primal EX and grind out the bosses, by about *maybe* the 26th week we all had our kirins. I found it the best way to do it, but make sure it's 5-7 people you know will be willing to remain in the group until every person has their kirin.

We're now moving onto the 60 primals.