It requires couple of times of re doing it. As many as 5 times.
Let the pipe defrost 80pct and put it back in freezer again. Repeat this procedures until the dent become less obvious. Add water if you think necessary. Sealing the stinger is the most difficult part. I suggest to use rubber ballon party and rubber bands to seal any openings.
The problem with ice freeze method : the shape actually change to fatter + rounder on the first and second chamber section.
If the pipe is badly damage ( already crushed like banana ).... ice freeze won't work.