I don't have an instructor, but I do have a drill.
Place the balls openly on the table away from pockets and rails.
Give yourself Ball in Hand,
Run the table in rotational order {1->2->3...}
When you don't have a shot, play a safety so you alter ego can't get a shot. Score 1 when you succede in not giving a shootable shot to your alter ego; Score -1 when you sell-out. Play yourself to 50 {or 100,...}
Early in the rotation rack, safeties are easy. Later they are not.
This practice combines long distance position and safety play.
{alternate game}
Place balls within 2 balls width of each other in the center of the table.
rest of the above applies
This practice combines delicate position and safety play.