i get alot of trashed out boards needing re-caps, - failed re-caps, I use flux alot.

Flux is also great used with solder wick when your trying to scrub off corrosion and trace rot.

i find that if you keep your tip really clean. And if your pads super clean…

and if you are not trying to re-install someones solder blobed up tantalums.

The 60/40 rosin core solder provides a sufficient amount of flux.