I was going to recommend sanding at first, but it would require a really good dust mask so you don't inhale lead dust. And at the end of the day, you'd still be covered in lead.

The best way I have seen to strip paint is to use heat. You can rent a paint stripper that is like a heat gun and paint scraper in one, those often work amazingly well. You can also use a regular heat gun and paint scraper at a much reduced speed.

I wouldn't recommend solvents because you will need to use a large volume and it would be hard to work on a wall that is covered with solvent without inhaling a bunch of the vapors.