A pea-sized amount of this soap will suffice.
I'll second this. A pea size amount would be about right.
I personally don't find that anything special needs to be done to lather PannaCrema Nuavia. Using the full size container, I just load my brush on the puck like any other soap, and when I did have a sample of it, I just smeared some in the bottom of a bowl. Either method works fine. PannaCrema's instructions seem to overcomplicate the process.