I have a serious warning about his "meditation" methods:

He has been quoted as saying that sometimes these entities will "follow you home" afterwards, which can be quite scary.

I studied qabalistic ceremonial magick, and the most important step in any ceremonial working is the BANISHING. A ritual should begin with a banishing to "clear the space". A ritual should also end with a banishing. Any invocation/evocation (such as his mediation method) should be book-ended by banishings.

Greer's method is essentially an open-ended evocation with no closing. It essentially invites these entities into your life without the ability to send them away when finished. This is a serious concern and as excited as I was to try his CE5 meditation for myself when I first heard about it, I realized that this is a dangerous operation to conduct without a way to finalize the experience and ensure you won't be having unwanted encounters at unwanted times afterwards.