It may be unrealistic to expect to completely get rid of aphids. They give birth to live young, so their population can increase rapidly and dramatically. The steps you have been taking should be effective in keeping the population at a manageable level. Using low-toxicity treatments such as insecticidal soap, squishing them, or blasting them with water are good for keeping the population of natural predators, such as lady bugs, at high levels. Actually it's good to have a few aphids around to attract the natural predators. Another product you might try for managing aphids is spinosad, a natural insecticide.