As said patination oil is probably the best thing.
That said I have been asked to repaint lead work . To be honest I never think it's the best idea but trying to clean up seventy odd year old lead is probably more trouble than it's worth and besides the customers wanted it repainting. The old paint will come off pretty easily but one thing to watch is that it will have oxidised under the lead and you don't reall want to be breathing that in. You'll know if you do as you'll have a sweet taste in your mouth , the white deposits on the lead are a mixture of compounds but were commonly know as lead sugar.
I removed the old paint and cleaned the surface with wet wire wool , then primed it with Isofix pegaprim , shellac based similar to zinseer BIN then topcoats . As yet there's not been a problem and it hasn't come off but I dare say time will tell.