Methylated spirit (max 1 tablespoon per litre water) is often recommended to mix with soap for spraying against aphids here in Sweden. No spraying in sunlight, please! I tried this myself a long time ago, but got some foliage damage if I recall correctly and haven't tried it since. However that was with a rather strong soap solution, which on its own could just as well be responsible for the damage. I think I had just over 3 tablespoons of soap in that mixture, way to much!!!
In any case I think one would need to try this on a plant to plant basis, but yes it's very likely that you will get better effect against aphids. Not sure if rubbing alcohol would be better or worse for plants. The alcohol recommended in Sweden is the most commonly available here, called "Rödsprit" and contains 50-75 % ethanol among other things.
