iPA is next to useless when it comes to dissolving dust because there just isn't that much organic crap in it that it can dissolve. Might work well with flux or some sort of oils/greases, but that's it. (And it will probably also dissolve most water soluble minerals, but much slower than water).
An ultrasonic cleaner might loosen the dust from the boards, but those things can also kill solder joints...
Also, if you use water use either demineralized water from the beginning or wash your boards with A LOT of DI water after you cleaned them and when they are still wet. Otherwise, you'll get all sort of nice minerals crystallizing on your boards, and most of them form conductive solutions when they get wet (humidity)->no bueno. And no, just rinsing it with iPA/other organic solvents doesn't substitute the need for DI water.