I think that a copper sulphate soak is a good recommendation and also agree with the poster that mentioned it may be hard to solve this by liquid application alone, as sometimes central sulcus thrush that bad is caused by contracted heels.
Durasole is worth trying if the above suggestions don’t work. Mine live in mud almost 365 days a year. Durasole is the only thing that seems to keep thrush at bay. I like to paint it on and let it sit for 5-10m. If it gets really bad I paint it on and wrap the hoof, it lets the Durasole spread without getting worn off by walking.