Yup, you really need both extraction methods to get the full deal. One of the best methods is CO2 extraction and a few days ago it just clicked that in the old days that was so easy. Take some Vervaine, honey and water add some yeast and bingo.
You end up making a kind of Vervaine Mead, the alcohol produced will extract some, the toxin from the alcohol will enter the vegetable matter as outlined in my Vodka post to allow access to more, and the byproduct is CO2 which extracts even more.
Also no cost of Vodka involved. 23-28 days you will have an Elixir that is multiples more powerful than any other extraction method.