Herb the Dishonest Milkman

Herb's trick was to line the outside of the milk crates with expired product. Then he filled the middle of the crate with expensive dairy products, such as cheese and yogurt. When he stacked these crates, there was no way to see these perfectly good products inside. He always waited until the clerk was busy with a line of customers before taking out the returns. On his way out to the truck, he would yell to the clerk something like "I've got 5 quarts of 1%, 8 quarts of 2%, 5 quarts of skim, and 3 pints of creamer!" (In fact, Herb would also have around 5 blocks of cheese and 6 pints of yogurt.) There was never any problem with anyone stopping to check, because, after all, Herb was charming and worked hard to make all the store clerks trust him. He would then sell this merchandise to other small groceries along his route, and pocket the money.

How many different theft techniques does Herb use here?