If your wish for somebody to be happy becomes sufficiently strong, then you naturally also want that person to be free from suffering, so in that way, loving-kindness leads to compassion. Hence, the lazy way to cultivate compassion is simply to master loving-kindness. Just do a lot of loving-kindness practice, which is easy and joyful to do, and eventually, your loving-kindness will be so strong that every human being you see, your first instinct is to wish for that person to be happy.
