So I've heard to use a soapy solution to give my infested little plants a bath. How strong should I make it? should I wet the soil also, or just try to get the leaves and stem? How harmful can the soap be- I suppose that depends on the plant... Any help- much appreciated as usual

I fergot!!! When you spray aphids with a heavy stream of water-doe sit actually kill them, or just knock them elsewhere to breed and do evil?

If you use Safer's Soap, the instructions should say which plants not to use it on.
Soap will actually kill the aphids, but simply spraying a strong stream of water only knocks them off the plant. The idea is that most if not all of them will not have wings and so won't be able to make it back to the plant.