I get strong sulphur thiol reactions when I chelate mercury. For these, chelation guru Dr Andrew Cutler recommends taking glutamine & glycine in a 2:1 ratio, which I find reduces symptoms by about a third. I also go off all thiol-ish foods till symptoms have retreated, such as tumeric.
Moly is also supposed to reduce symptoms, tho it didn't do a lot for me. Vitamin C is also recommended for this.