I've never used liquid flux in electronics soldering before, relying on rosin core solder, even with hand soldering of SMD components.
Some videos I've watched recently make me think this is something I should get. Bit what kind? There seems to be a bewildering range. Just one manufacturer I stumble on (Kester) makes dozens of kinds. Activated rosin, mildly activated rosin, non-activated rosin, alcohol-based, inorganic acid, etc. The halogen-free or not.
So, what's the best choice for hand-soldering SMD components?