Daryl, That flask was made by the original owner of October Country, Mort Fadum. I bought the business from him in late 1983 and ran it until 2005. I believe he started it in July of 1977.
Mort's original process was to pack the flask with sand. I continued that procedure for a few years until Dave @ Track of the Wolf commented that it took forever for the sand to work its way out of the leather and it could be an abrasive on the tubes of a shotgun. After that little chat, I switched over to using #6 Nickle plated shot.
Do you need plated shot for this procedure? Nope, not at all. It just was what was available at the time. Interestingly enough, that original 3 pound coffee can of shot is still being used to this day.
I found warm water worked best for me, but I think that was just better on my hands when doing a production run of a couple of dozen at a time. I really don't think that the temperature of the water makes a difference.
Hope this helps,
John (Bigsmoke)