Since my first post about Softimage and OpenVDB was more of a brief overview than a tutorial, I decided to create a step-by-step guide on how to create a .vdb cloud-like grid with Softimage ICE using Mr.Core's (Oleg Bliznuk's) compounds and explain how they work on the way.
To follow the tutorial, download the compounds and connect the extracted workgroup in Softimage (File -> Plugin Manager -> Workgroups -> File -> Connect):