Old-Skool training IMO is just training with a bar and weight, or other simple implements like sandbags, tires, logs, etc. Next to no machines (simple cable machines were available in the 70's) and cardio was done outside.
Old-skool routines were simple periodisation, no time under tension or other garbage. BB'ers trained with basic routines, added weight as needed and mixed strength and pump-training. American based PL routines were generally linear (look up Coan/Hatfield routines) and other commonly used PL routines like WSB and 5/3/1 are all based on old soviet periodisation.
Read "Dinosaur Training" if you want to get some good ideas about Old-skool lifting.
Most of my training is based on Old-skool ideas and, aside from the addition of band work, uses strictly old-skool equipment. Most commercial gym equipment is unnecessary, if Arnie didn't need it the nobody else does either. Old-skool ftw.