Capt. Craig: Regarding the burnished spots,.....by mistake while testing a biodegradable stripper called Multistrip (purchased at Home Depot), I saw that some screw hole staining (from cheap stainless screws) on my teak rail was made much worse by sanding the area, but then the stain was lifted very nicely by the stripper. Looks OK now.
If you are sanding the charcoal, for sure it is bound to stain beneath. Just thought I'd mention this.