The hextadon is the big mastadon looking animal found in the snowy area it has huge tusks and is rather large.
An easy way to do it is go to the winter area and drive around until you find a Hextadon, park your deuce near a tall ledge close by then go back the the Hextadon, Shock it a few times until it is stunned, then hop on its back and ride it. It may be tricky to get on but if you have trouble just move around it until you find the que to jump on its back. Move him underneath the same ledge where you left your deuce, it helps if you point him right towards the wall, then jump off hop in your deuce drive back up to the top of the ledge and jump off I found this strategy much easier than trying to lure the hextadon near a ledge.
Another Strategy is if you have done the beast master missions and get the hextadon as a summon. Summon one underneath the ledge and it will not move at all then summon your deuce and jump over it.
Comment if you have any questions I will change the solution as needed.
Honestly I gave an easier way to do it than that video why vote negatively?