I recommend using a scorpion to tame it, pump all levels into health on the scorpion. Then just attack the Rex but with 10 to 20 seconds in between hits, DO NOT pump anything into dm. Also this is what I use to tame literally everything, and it doesn’t even cost anything. Pls put this up in chat for everyone to go “oh that’s not a bad idea” 👌😄👍
If you use the bear trap strategy which is if you lead it into a Dino gateway that is shaped in a triangle and with a bear trap in the middle (Large Beartrap) and when it is stuck you must put a dinogate behind it to trap it and then knock out.
If you wanna an easy way to bring a rex to trap or below a cliff, tame dodos or any small creatures a pteranodon can pick up. They will follow if your carrying any small creature, I have done it with not only rexs but raptors as well.
I hope this helps you to bring the dino you want to tame into a trap.