A pass can feel straightforward on the approach and suddenly get crowded at the apex. Once a car is alongside, both drivers have a smaller piece of track to brake, turn and accelerate on. You can get used to that space before you have to judge it in a race.
Practice the two lines separately
Pick a wide corner with clear braking references and agree with a friend to start at a moderate pace. First, drive the inside line on your own. Try braking early enough that you can hold that tighter radius through the exit. Then take the outside line and see where you can pick up the throttle while leaving a lane open beside you. Notice which reference points disappear when you approach from a different part of the track.
Put two cars in the corner
Run the same corner side by side, staying in the lanes you rehearsed. Swap positions on the next lap. If you lose track of the other car, hold a predictable line and give it room until you can confirm its position. The next drill starts with the trailing driver slightly behind. Call off the move early when you can no longer establish the overlap your series requires.
Watch one replay from both cockpits. Check where the gap tightened, whether either car had to leave the track and how early the driver who backed out made that choice. For a breakdown of the phases of a pass, see the iRacing racecraft guide.
Try the drill alongside your start and rejoin practice if you're preparing for your first race.