Lecithin is an "emulsifier" that has some positive effect on the brain that I'm not 100% certain of. Something to do with beneficial fatty acids. You can buy it at pretty much any health food store. The granules are cheaper than the capsules. I use Solgar brand.
I started using DMSA per Cutler's original protocol, where he said we should start out with DMSA for three months to lower the metal body load, before adding ALA that lowers the brain load as well. DMSA cannot pass through the blood-brain barrier, that's why you need ALA to take care of the brain.
Anyway, in my experience, that was a good thing to do, because I DEFINITELY felt body chelation symptoms while on DMSA alone, and I also definitely felt strong brain symptoms once I added the ALA. Also, DMSA chelates lead as well as mercury, and I was pretty sure that I had lead poisoning because I had been drinking lead-contaminated tap water for years without realizing it.
DMSA is not so expensive if you buy it in at vrp.com. I bought the 12-pack of 50mg capsules, and I figure that should last me basically until I am done with chelating.