Re: Can I teach herding cows myself?
For teaching that'll do, start with a play session of some sort, like playing with a ball. At the end of the session, say, that'll do, pick up the ball and stop play. Sit down and shift focus, say, to petting and praising, as long as it's quiet pets. Use it at the end of any vigorous activity, like, jogging, say, before a period of rest.
For left and right, you can use the word command while you're walking on leash with the dog, then go gradually to the right or left. Remember, though, that you are teaching the dog what his own right is and his own left is, so that when you add hand gestures, and the dog is facing you, his right will be your left and your left will be his right. Sheep people use away and come bye instead of left and right but from what I have seen, sheep are worked in a much tighter pack than cattle would be, for a wide variety of reasons, size, speed, etc. They are also worked much closer to the shepherd than cattle could or would safely be worked, (cattle can knock you over so much more easily than sheep can and they can step on you a lot harder, never mind kick with a lot more power, and we're not even talking horns) so your style with cattle will need to be different. Cattle are worked more slowly, just to begin, and the style is more pragmatic. You don't have to look pretty, you just need to get the job done.
Also, just for giggles, you might get the pbs special where a rescue bloodhound is taught to track and a rescue bearded collie is taught to work sheep. It'll give you ideas. I don't like the concept of putting the dog in a pen for the night and leaving him and just working him during the day, with no relationship beyond the working one, but I know a lot of old timers felt that way. I don't think that will get you anywhere you want to go with a German Shepherd, but you can enjoy the poor lady's struggles with Herbie.
Good luck, khawk