The last time I went out there was 20 plus years ago, far fewer resources on the internet. We had a local with us who had figured out the logistics and we worked off a map (nothing like a Farout ap). I am mostly a northern new england hiker and its nice to get out into new territory. Of course with this spring's very rainy weather in northern new england, I have some recent practical experience with rainy hiking.
The logistics for the Wonderland trail would be simple but expensive, rent a car at the Seattle Airport, drive to the Ranier, stash one or two resupply cans at one of the three trailheads and park the car for 10 days. Expensive but simple.
BTW, we found an airport hotel that allowed us to leave bags in storage during out trip, this allowed us to change out gear after the backpack and prior to trip in the Olympics.