Hi, oh I'm not really knowledgeable. I have had those symptoms you mention very occasionally but I wouldn't class them as brain fog which is a reduction in cognitive/intellectual ability (thinking/concentrating/remembering) though that has a chemical/physical basis too.
I believe brain fog is one of the last symptoms to go completely maybe as it can take a while to detox the brain (esp if something like mercury is the underlying problem) and correct EFA and mineral deficiencies. I don't know if the same applies to the symptoms you mention, I suppose it depends on how deficient you are in B vits and EFAs (esp omega 3) which is linked to tingling and buzzing.
Although most people have very similar symptoms it's highly individual and not always predictable as to how someone makes progress. It sounds like you are on the right track though if those particular symptoms are lessening :-)