Something i like to work on with my younger cousin (he's just beginning) is teaching him to make the chord he wants to master, press hard against the strings with all fingers at once, then relaxing without taking his fingers off the strings. This will help develop that muscle memory he needs to instantly pull the chord from his brain.
Another way I like to train him is by getting him to lift his fingers right off the guitar, mainting some shape of the chord and then pressing back down all at once. You can pull away farther and farther the more comfortable you get.