1. Wait for it to crawl in the desert,then throw a grenade at it

2.it will go out and it would be a little dizzy that's when you have to go and ride it

3.control it to hit rocks and the torpor would start getting higher (metal + crystal do much more than normal rocks and probably also others like obsidian or sulfur would do the same) and try to not get stuck or fall because you'll have to do 1 and 2 again same happens when you stop bumping into rocks for a while and do the same until it's knocked out

4. Feed it raw mutton or exceptional kibble

5.bonus tip , before starting go on a flyer and mark every pile of metal and crystal you see in the desert,a 150 even with hitting a lot of metal and crystal rocks still took more than an hour imagine doing it all with normal rocks