Initially, we hadn't planned to visit Shirakami-Sanchi on our first trip to Japan. But I realised that we had one day of our 14-day JR Pass possibly going to the waste, so I added a few extra bullet train trips to our itinerary. (We definitely got our money's worth from the pass!)
We choose to visit the Aqua Green Village area, with the aim to hike to Anmon Falls. The falls can be reached by public transport and are within the buffer zone (all that you can visit within the permit required for the core).
After visiting the Hiraizumi WHS, we continued north mid-afternoon and spent the night in Hirosaki. (We took the 2:51pm local train from Hiraizumi north to Morioka, the bullet train to Shin-Aomori, then the local train to Hirosaki, arriving at 6:12pm.) We arrived too late to buy bus tickets for the next day, so returned fairly early to the Konan Bus ticket office at the train station the next day, concerned we would miss out. Not that we needed to worry, as the tickets aren't reserved and there was hardly anyone taking the bus on the rainy day. The bus starts from the bus station before stopping at the train station, but the return bus only returns to the train station, so we stored our luggage there. The bus only runs up until the end of October, see the timetable with the infrequent services here: http://www.konanbus.com/travel/shirakami.html.
While doing some last minute research, I grew concerned about undertaking the Ammon Falls track, coming across notes that helmets (available to hire) are recommended, plus a guide. Not that I should have worried. When we arrived at Aqua Green Village, we discovered the track was closed, following the recent typhoon. (Plus the warnings mainly only apply if you're heading to the top waterfall, fall #1, the track to falls #3 then #2 should be okay for most people. There is also a recommended donation of 200 or 300 yen.)
We instead hiked the World Heritage Beech Forest track. The map showed that this also went inside the buffer zone, and the couple of kilometres in the rain on a muddy track was enough for us. Not that we were the only visitors - there were also a few bus loads of Japanese pensioners who completed it around the same time. Afterwards, we considered have a soak in the hot baths, but instead caught the earlier bus back to Hirosaki, getting back to Tokyo around 6pm rather than our expected 9pm. Do head inside the main building though, as that's where the plaque is - plus the lunch options looked good.