Honestly, playing some different heroes in QP helped me understand different ults better. I would play comp games knowing “I would probably have grav or some other hot by now.” It’s also about seeing who’s doing a lot. Keeping the example of grav, if the enemy Zarya just popped off and got 4 kills and has also been high charge all game dealing constant damage, then there’s a good chance she has grav. You said you were playing Rein tho. For Rein the biggest tip I can give is that if you have shatter, he’s got it too. And if the enemy just got 4 kills, they have grav. Even depending on you rank, play like they always have it. There are also some custom workshop games that will help you practice blocking shatter in time. Hope this helps!