Good morning John,
Thank you for starting this thread!
I am very pleased someone took the time to film this, as it is very much a lost art as you know.
I wish they would have shown the use of those grinding wheels, but using the gauge, they maybe didn't use them as much any more.
If I remember right, the man with the smaller hammer was called "the master of hammers", and where he struck, the helper with the big hammer struck.
I timed it roughly and yes, they had about ten seconds of welding heat, like we were always told!
Thank you again my friend.
Hope to see you again before too long!