Fr tho... The cheapest but most dangerous way of taming a Rex is to find a high level tame that you can access your weapons from. I use Thylacoleos and level up their health and stamina so that I can get the Rex to chase me while maintaining a safe distance and get a couple shots in and run do it until he begins to run away from me. Another more expensive way is to make a trap(which you probably know about) but create either a metal or stone trap of 3x3 to 4x4 foundations and doorways about 3-4 levels tall around the edges. Then place ramps on one end for the dinosaur to be able to run in. Get a flier with good health and lure the dino into the trap. This works on most of all the big dinos from Thylacoleos to even a Giga(if you tame the giga in this trap be sure to use metal bc they cam damage stong and shred your guys face). Its an expensive build, but it works for raising eggs, and taming ;). Also be sure to know if the dino cant damage it or escape from the doorframe