My fingers are yellow again from squishing aphids. I find if I do this once a day and wash off the milkweed that it kind of keeps them under control. What I meant by kind of is that they don't get to multiply as fast.
I don't want to spray anything (even organic pesticides--for example, Safer soap) right now on the milkweed because there are caterpillars and eggs. I do have to be careful that I'm not squishing tiny caterpillars or eggs while I'm squishing aphids. It is amazing how fast those aphids multiply.