In article ,
"Michael A. Terrell" wrote:

You want a good, mild RMA flux, not just liquid rosin. My favorite
was Kester 1544, but I think they dropped that formula now that they
concentrate on reflow solder products.

1544 is still around. A gallon is about $50 and would last your average
DIY guy about 800 years, if it weren't for the fact that the volatiles
seep through the plastic bottle.