I don't think you understand the difference between soft ash and hard metamorphic rock. I've been to Mt. St. Helens, and looked at those canyons. They aren't what you were told they are.
Notice the walls slump when they get more than a few meters high. And you don't see these:
Entrenched meanders only happen under certain circumstances. And old, slow river wanders because erosion speeds up on the outside of curves, and soil is deposited on the inside of curves. Over time, the river wanders and snakes into loops. If the land is then uplifted, as the grand canyon area was, the river is "rejuvenated", speed up, and becomes locked into the bed, cutting deeper and deeper into the rock.
This process is being observed today, so we know how it works.
Here's Sioux falls, in South Dakota. The river has been running through here since the last ice age. The rock is quartzite. The "canyon" is a few feet deep.
The condition of the trees is a tip-off. They were actually not woody trees, but lycopods, with a hard outer layer and a pithy center. The trees at Joggins are hollowed out; the pith decayed before being buried. There are often fossils of lizards and other animals in the center, showing that they were dead and rotted before being buried, which would eliminate them from a "flood."
There are similar polystrate fossils being made, not far from my house were decades ago, a dam flooded some woods. Most of the dead trees are still standing, and they are slowly being buried in layers of sediment.
Not knowing what one is talking about is a great disadvantage, yes.
It will. But of course, it's not what the YE creationist is hoping for.