Sorry, took a while for me to dig out my copies of Kelso's Shrug Book and Powerlifting Basics: Texas Style.
In Powerlifting Basics, page 50, Kelso suggests running them 3x8 on an incline bench as part of an off-season powerlifting cycle.
In the Shrug Book, page 13 (which was in turn an excerpt from pg 42 of the October/November 1968 issue of Iron Man, page 42) it reads
"Take a bar loaded to about 70-80% of your rowing motion poundage" with more to follow describing the movement itself.
On page 15 he recommends 2-3 sets of 8 reps.
If you can, get both of these books. They're flat out amazing.