I don't know why I haven't thought of this before. It's one of those obvious things that for some reason, perhaps because it is so obvious, doesn't come into focus.
There is an excellent online resource for those interested in Renga. It is run by two long-term practitioners of the art. One is Norman Darlington, from Ireland, and the other goes by the Moniker "Moi", from South Africa. Both of them are dedicated Renkujin. (Renku is the preferred name at their online location; it is the name more widely used these days.)
This is an online Renku Group and at this site there are Renga/Renku of various kinds being composed online, posts about theory, and notes about the latest goings on in English Language Renku.
I have composed a Renku with Norman in the past and found Norman to be a sure and wise guide. Any questions you have can be asked at this site and Norman, and other members, will be very helpful. My own abilities as a teacher are limited (that's generous). Norman, and several other people involved, in contrast, are excellent at cultivating a beginner's understanding of the form.
The site can be found at:
If you have even a passing interest in this form, this is the place to go.