I also read he would specialise on either the squat or deadlift for weeks at a time. When he was working the deadlift he would do that lift almost every day to the exclusion of much else. He would then switch to squats and progress on those like that too.
Similar system to John Davis and Doug Hepburn from what i've read, they would typically specialise on one big lift at a time. However both Davis and Hepburn would specialise on a quick lift and always squat as an accessory.