Regarding the alcohol, it depends on how you intend to dry the board. If you use an oven to dry the board like I do, then I don't think alcohol is needed and actually I wouldn't stick an alcohol-soaked PCB into a hot oven.
If your oven cannot go low enough to avoid damaging the board (75 degC or so) and you need to dry it at room temperature, then washing the board with isopropyl alcohol can be a good solution since water on its own will take long to evaporate. In a 75degC oven for just a few hours, close to 100% of the water should have evaporated and if the water is demineralised/distilled, then there will be no deposits remaining. The heat will make sure that all the water is evaporated quickly, even inside various cavities.