Laurie- Pickle then sonic for a good while then steam. It’ll come
When flux mixes with yellow ochre or other anti solder compounds it
makes a mess. I try not to use it. Just use good torch control to
avoid solder flowing where you don’t want it.
On another note. I really don’t like threaded posts. They are
irritating to push through the ear. It can be like barbed wire. They
loosen and strip out over time and have to be tightened or replaced,
the threads trap ear gunk and bacteria as well.
I prefer the Protektor or Guardian locking posts and nuts. You can
pull a tight turtle neck sweater on and off without loosing an
earring. The can also be shortened at the base and then have the nut
click in at the longest notch so that the post doesn’t stick out much
past the smooth nut. You can wear them 24/7, sleep in them, and talk
on the phone without the post sticking you in the side of the head.
Have fun and make lots of jewelry.