Verified answer

Nothing beats constant practice. But if you meant that he has trouble distinguishing an Americana from a Kimura, which is common for novices, then just let him remember that, although both are called keylocks just the same, it's an Americana if the forearm points towards the head or is above the shoulders and it's a Kimura if the forearm points to the direction below the shoulder or towards the hips.

If the fist points UP ..it's Americana. If it points down, it's kimura (kimura is sometimes erroneously called a hammer lock because of similar positioning)

Roses are red, violets are blue..

Learn the damned technique, or someone will use it on you!..

That should motivate him.

Practice and more practice

just practice

not that i know of. they are not terribly difficult submissions... just practice with him