In reply to raliadsa skcalbwah:
There is a bus that will take you down to train line in the valley. From there it is fairly easy to get a train up to Chiavenna and then the Swisspost bus to Bondo. The swiss buses are reliable and frequent - you can download the SBB app and it will tell you what you need to know. Last year, we drove up to San Martino and left the car at the hotel at the end of the road (5CHF for 2 nights) and jumped on the bus from there. It takes a few hours so we did that the day before walking up to Sasc Fura and stayed in Chiavenna - it was raining so we didnt mind taking our time. The buses aren't very frequent (maybe 1 an hour from 10-3 or something) and I think the last one was about 2 or 3 pm. I'd show up in the morning prepared to wait up to an hour for the bus and go from there. This is an italian bus so the info isn't available like the Swiss ones.
If you're pushed for time, like getting to the hut for dinner, then maybe splash out on a taxi.
Dont forget it is now mandatory to wear a mask on swiss public transport. I cant speak for Italy.