Edge Rails Nested has_many :through Association

So this functionality isn’t supported natively in Rails 3 (or any
versions before that for that matter) But I had found a work around
via this blog post:

This didn’t work on Rails 3 because it wasn’t able to properly build
the query from the join with symbols. I was however, able to get it to
work using a singular symbol for the model relation to the child, and
then manually writing the SQL from the next nest up. Is this the most
efficient way to go? Or am I missing something here?