My understanding is that the leftover product is Lead Acetate. Really nasty stuff. This in no way belongs in your normal trash or disposed of improperly. This is NOT just liquid lead.
If I understand correctly lead acetate can be absorbed through the skin and the vapor through the lungs. It should be disposed of as highly hazardous material and handled with extreme care.
Lead Acetate MSDS:
https://www.atmos.umd.edu/~russ/MSDS/lead_acetate.htm
My precautions:
Use glass containers: one for the dip, and one for fresh water rinse. I save peanut butter jars for this.
Do this outside! Away from pets and kids.
Mix only what you need. I do about 1/2 cup of each for my TBAC 22 Takedown.
I wear long sleeves, long pants ,shoes, safety glasses and a painting breather mask with charcoal canisters.
I wear Nitrile disposable gloves
Have a piece of coat hanger to pull the parts, to place in the rinse.
When finished, I pour kitty litter in both jars. Careful that you have enough room because it will expand. Leave lid loose until it stabilizes.
Tighten both caps, tape around caps with duct tape, mark “Lead Acetate- will kill you!!!” on another strip of tape. Place in separate sealed ziplock bags.
Deliver to hazardous waste facility. Ours here in Laramie takes it free of charge.
Throw away gloves, coat hanger etc in outside trash.
A side note:
A young University of Wyoming student & fellow long distance shooter friend of mine here locally got lead poisoning so bad, that he had to have his folks come from Oregon to drive him and his vehicle home. He has yet to determine the source. I personally suspect shooting or mishandling of something shooting related......