Kent uses Sal Ammoniac for flux, but I don't know anything about it. I neutralize after tinning, and do a phosphoric acid cleaning after filing the lead.
The way Kent demonstrates it, Sal Ammoniac seems like a better flux than anything I have used.
my grandfather & i hammered (he did most) on wood copper & brass to make little spoons when i was 10 or so.
practically chewed asbestos, died from broken hip in his mid 90's.
Ammoniac key word of the day?
I can tig weld up some edges where needed , but others I'll wimp out & use a little harder filler. A little hard to do perfect complex metalwork at home at night after work without having better tools or workplace or enough consecutive metal work practice.
Metal 2 Metal is very good stuff for the application, but really, dont just let it sit overnight and get at forming, just let it set up and start working it. The longer you wait the harder it is to deal with.
We used to have a guy come in to patch our lead lined anodize tanks, the tiny little torches he kept in his pocket did such beautiful work. McMaster Carr still sells bar solder for 25 bucks a pound stick, that is still 60/40 so its easy enough to find and try.
Right now we are replacing both the quarter panel and roof panel on a chevelle. Vinyl top and a garage collapse. Get to the between seem from the AMD roof and Goodmark quarter and it looks like a 2" strip of metal welded in would be a better choice, still dont know which way we are going to tackle that. I know the lead stays more flexible, but metal 2 metal is so hard, I cant see it being better than welding the two together as hard as it gets.
The large soap bar block of SA christmas gift wow'd my dad. His dad likely used same thing in 1920's here.
If all my dad & i do is make our soldering gun tips we rarely use better then new, it was worth it.
Will need a little harder filler for the edges of this aluminum spoiler also after I tig it together. May just bond it to my existing aluminum cover so I don't warp the F out of it & use some eurosoft I have for the joint area.