Definitely the biggest thing to do with green horses is grids! Set out about 5 jumps in a row ranging from a bounce to 1 strides to 2 strides and set the mm up in order of height so start with just a ground pole in the first then a small cross rail in the second, a bigger cross rail on the third, a vertical in the 4th and the biggest vertical on the last. Obviously you set the height to how much your horse knows and you can add as many jumps as you want but this really gets the horse jumping of the hind end and teaches them to go straight. It definitely is the best thing to do with a green horse.
try waking into jumps and then he can climb over, then once he is relaxed try trotting and landing in canter.