You would appear to be well off the beaten track, since neither town is mentioned in my guidebook! This means you are unlikely to get feedback on these forums from anyone who has been that way. I also suspect that, since you found nothing online, the route you want to take is no done by first class buses (although both towns are apparently served by Primera Plus). There may be a second class service, either direct, or bus hoppingvia Zamora and/or Uruapan. After all, everywhere in Mexico has buses. Since you are already in the area, surely your best plan is just to go to the bus station and ask.
By the way, Uruapan has its annual craft fair soon: a big event.