I don't know of the Walstad method, but I've heard of it quite a number of times recently. I've only tried the "nooby" method (lmao) and DSM right now.
Not to derail the thread, Diana Walstad is a microbiologist who wrote a book called Ecology of the Planted Aquarium, that looked at the science behind using soil with a sand cap, low lighted, planted aquarium. She began testing using soil in aquariums because she noted most lake and streams have soil substrates.
This was before ADA aquasoil, or any of the new aquarium soil substrates that are intended to hold ferts. According to Walstad, the soil is the catalyst for breaking down excess food and fish waste into nutrients for the plants.
It's not a perfect system, but it did work really for me and if you're looking at very low maintenance (I did 20% water changes maybe once a month, and kept the tanks topped off... that's it) then I still recommend it.
But, the downside is that with any capped system, you wouldn't want to move plants around too often after it's planted.
Ok, sorry for the diversion... back on topic.
I'm looking forward to this tank too!