Be sure that you get the White-out that is labeled as NON-flammable.
It actually can be thinned with water. It will get thick, so mix in
a little water, drops at a time, until it reaches the consistency you
like. If it gets on your skin, wash off with water. After soldering,
just put the piece in pickle as usual. Unless caught inside chain
links, White-out comes off in the pickle. Normal ventilation during
soldering is adequate.
I like using White-out because it’s ready to go and is easily
painted on, plus it dries quickly. It seems to protect soldered seams
as well - at least that is my experience.
Definitely AVOID the flammable stuff.
Judy in Kansas, who is missing out on a loverly afternoon… and
tomorrow is predicted to be cold and blusterly.