We ascended the ridge between Plosky and Ostry Tolbachik from the south, camped on the ridge at 3200m (very windy!) and ascended along the ridge the next day. Descended the same day via Plosky, going round the crater clockwise.
Note, there supposed to be a bergschrund in the lower part of the ridge but in July it was filled with snow and we did not actually see it.
Great view - into the crater as well as the surrounding scenery. Could see Kronozky Volcano in 200 km distance