I've been lurking on Strong First forum and website. Strong Endurance is kept in deep secret, to the point of actually being funny. I guess they will milk everything out of seminars and then come out with the book.
In any case, the method is not that complicated. I went once more through Khozhurkin's book, the part that deals with training. The idea is still as mentioned before: lift for short sets avoiding lactate production, rest sufficiently, repeat for prolonged period of time. You can gauge the intensity and recovery by Maffetone HR estimate - don't exceed it during the set and let HR go 20 - 25 beats/min below it. Some of SF posters use snatches, and from what I can gather there are numerous protocols in the seminar manual using one or two lifts doing essentially the same thing, working out for an hour at lowish HR.
Or, you can work in series. For example, five sets of 10 snatches, rest one minute between, then longer rest, repeat five sets and so on. It makes sense if you decide to work with heavier load. From my experience with GS fatigue tends to add up from set to set if you lift heavy, so in order to avoid lactate accumulation (which I think is the cause of accumulated fatigue) you have to take longer breaks from time to time.
The progression is decreasing rest between series, decreasing rest between sets and increasing reps per set. In Khozhurkin's book which is devoted to pullups the goal is to do 50 - 60 pullups in four minutes. For GPP it makes sense to stick to increasing work capacity over an hour - increased load and maybe cadence, keeping rest intervals the same while maintaining the same low(ish) hear rate.
I am planning to try this with double KB jerks, my favorite lift. Not sure yet with 16 or 20 kg (have to try). Or maybe snatches, they may be easier to use with the HR monitor.