Griffs are very smart, very sensitive and sometimes very stubborn! If the training session becomes too repetitious they become bored quickly. Same when you give commands in the same order each time. They will then anticipate and do something before you ask.
Try making a game out of it, with plenty of positive reinforcement. When they anticipate I change direction and ask for something different. I ignore anything they do that I haven’t asked for.
Following this pattern most griffs are quite easy to train as long as I kept sessions short and frequent. Some are more difficult than others, depending on the individual.