One of the quickest ways to eat greens is a "wrap" Take a chunk of something like banana, date, avocado, tomato, etc and wrap it in a few pieces of lettuce really tight... It ends up being about 4 bites worth of food, total, and you get maybe 5 of those out of a head of lettuce. You can also do the "wrap" with nothing in it, but many people don't like plain lettuce.
also, green smoothies! I just make banana smoothies, but you can easily add 1/2 lb at least to a meal worth of bananas and that takes almost no time at all.