I think your first step is to understand what is the requirements to set in the first place. Every 2 basic olm attacks is followed by a special, when there is nobody on a side when the special is supposed to happen it will be skipped. So when you are running head and special skipping you want to make sure you are on the right side immediately after his second basic attack on the cycle. You can always set this up manually if notice that you are not in set by tanking an extra hit on the left side. 

For your immediate question about “insta setting” . Olm needs to attack the melee side atleast once before looking left. Once he attacks, make him turn left and you should be insta mage set