Hmm, I still got plenty of this blue stuff that looks like washer-fluid, and is a fluxing-demon. Fizzes away as you’re cooking the joint, even a light dab lets the solder wick its way into the wire and make a nice solid joint.
Fiik what brand/formulation it is, as the place had it in a gallon jug and they let me fill a glass juice-bottle (½pt or so) with it. Still got over half left, as just a teeny drop does the job.