I use a mixture (about 50/50 -- not critical) of acetone and ethyl alcohol (denatured, grain, analytical grade, etc.) and an old toothbrush to remove flux. The acetone is probably not required. I add it to make a slightly more aggressive solvent; however, if there are plastic components susceptible to acetome on the board (for example, certain connector types), I omit it. Some people use pure isopropyl alcohol and omit the acetone.
The important thing, I believe, is to avoid water. So, whichever alcohol you use, try to get 100%, not 70% or so. John