A great exercise to target the lateral deltoid head is the behind the back band lateral raise. Band resistance is highest at the top of this movement, so this exercise hits the middle deltoid pretty hard.
The Potpourri Routine is a forgotten bodybuilding workout that predates the invention of sets. It is the 1930’s version of German Volume Training and was a favorite of John Grimek. In potpourri training, you perform 6-10 exercises for a muscle group, but only one set per exercise.