Soap and oil are generally for hard-bodied pests, aphids are soft-bodied, which is why iso. alcohol works on them.
Here's some effective home remedies that Ray has collected:
First Rays' Home Remedies
ETA: That's not to say that Safer Soap wouldn't work, I've just found that the alcohol works better, and I don't have to pay for it. Neem oil is great- kills some pests on contact, and makes the plant taste bad (topically).
Get a systemic like Bayer's 3 in1 for roses, works great for keeping disease and pests away- again, makes the plant taste bad, but for 30 days and is safe for orchids. A lot of higher-up growers I know swear by it.