Dave, I'm not Jhan but to answer your questions...there is a theory in homeopathy called Hering's Law that the body heals inside out ie from the deeper internal organs to the outer organs and also from top to bottom. See the following page...scroll down to "The Healing Crisis and Hering's Laws of Cure"....
I certainly feel this is true...I feel better when I get skin rashes as toxins are being pushed outwards instead of bothering the deeper internal organs though it can also mean the skin is overloaded which needs to be dealt with.
As far as brain fog goes yes it will go! It will be better on some days and worse on others as toxins are moved out. Often brain fog is the last symptom to go for some people. Supplements help a lot but almost everyone will experience an exacerbation of symptoms. For some lucky people it may well just take change of diet, correcting mineral imbalances and EFA deficiency, increased absorption of B vits esp B12 which gives mental clarity. Liver support helps too.
For others like myself mercury detox is the answer.