Hi Sonia,
I'm glad you have come to this site to share your interests !
Since those who practice what B Moen teaches believe in communication with spirits, then I guess that makes us spiritists, as is/was J Greber. Greber's first book appears to be the only one translated into English so far--and we US members here are notoriously limited in languages.
I tried to read Gerber on the web but Google mainly finds him tangled up with Jehovah's Witnesses--? I couldn't find much on what he taught. Many folks here don't rely on mediums, even someone like Gerber's wife, since we make contact ourselves.
I regret that those are my excuses for not being able to discuss his ideas.
However if you'd post more on his ideas, I'm sure folks will have comments/opinions.
Bets