If your strictly going for the achievement or trophy/trying to line up a huge ultimate it will just take longer.
His ultimate is complex (you know this) and if you focus on getting the quad kill you’ll only end forcing it when you shouldn’t, and I found myself is super stupid situations trying to force it.
Focus more on game sense than anything else. Lining up the four skulls is easy, staying alive getting the shots off unblocked is the hard part (as there are so many counters. dva, genji, Zarya bubble, the list goes on)
Obviously flanking/high ground seems like obvious tips but from personal experience I’ve gotten 4-5 kills ulting in the middle of the point a few times. Im still not that great but I learned watching the pros.
The best bit of advice in terms of game sense has to do with priorities.
The best time land it is when there is something more pressing for the enemy to handle that they can’t ignore.
When they hear “it’s high noon” they’ll almost always turn attention to that as it cannot be ignored or the potential is they all die( depending on your positioning).
Your going to have to wait until they can’t do that (they are forced to ignore you or die). like wait until they are super pushed up in the fight. Have committed on a dive. And won’t be able to switch attention to you because they over committed to whatever they were doing.
Hard to time, but much more successful than forcing the ultimate when you see 4-5 people all lined. Because they could all turn and quickly address/counter you without any other thing they need to focus on.
Also Ulting behind a friendly Reindhart sheild is underrated. Your getting a lot of protection and you can get kills off from very powerful spots (in the open) you never could have before.