I remember some years ago ! when I was making PCBs, these had a mix of through-hole and surface mount components soldered by hand (for different functions)after flow soldering. Flux was cleaned off with IPA and toothbrush. They were then put under a warm, not hot, running water tap, then dried off with a compressed air gun (very noisy!) then left in a warm place overnight to dry off. As long as they were completely dry, all were good.