The Drill
Every training session on the 707 and the 727 had a dutch toll drill somewhere along the line.
The trick was to aggressively move the control wheel to the stops towards the wing that was coming up, then back to neutral (level) position.
As soon as the other wing started up, you did the same thing. It usually took 2 or 3 "slaps" as we called them to get the dutch roll stopped.
As I recall, they were called "slaps" because when you moved the control wheel hard one way or the other, it caused one of the spoilers on that side to "slap" up to assist the aileron"
Did many of them this way, and it worked.