Flux, liberally applied, is the sudo of soldering. It lets you force your will and make the solder do what you want. No one ever uses enough. I always have either a pen with a felt tip, or a syringe of chip quik.
It (a good proper flux) is what most people are missing when they struggle with SMD, the flux makes the solder almost magnetic and it jumps perfectly to the pad and the component. Mess up, make a bridge or bad connection? Add more and wave the tip through like a magic wand. Poof. Fixed.
Thanks for coming to my Church of Flux presentation.
For sure. If you watch x device repair videos they tend to flood the general area with flux and it works to great effect.
I do the same. Flood and get the joints perfect, then clean with either IPA or a can of flux off.
And don't ever think the flux core within the solder will be enough.
The flux in flux core solder is completely useless for PCB soldering, It needs to already be on the PCB when the molten solder meets it because its main purpose is wetting the surfaces and reducing the surface tension of the solder so that it flows easier. Properly fluxed solder behaves very differently from the stubborn solder balls people normally experience when starting out.