i would figure dmso would require only weak reducing agent to be converted to dms, i was looking for a free-energy table to see if Sn(II) would reduce it under basic conditions (acidic condition must be avoided becuase the creation of methylthiol would be undesirable and stinky.
if you know where a extensive thermo/free-energy table is on the web please point me out.
but if this (or someother basic aqueous reduction) were to reduce dmso to dms, it would presumably hydrolyze to form MeSNa, and MeOH.
after isolating the MeSNa, reacting this with a weak oxidizing agent (perhaps excess sulpher), should give dimethyl polysulfide, which could be extracted into a non-polar solvent, and would presumably make a good methylating agent.
actually a way to reduce dmso to dms , without hydrolysis in the presence of excess sulpher would be more desirable, as it would allow you to directly create the dimethyl polysulfide. and would only require half the dmso to create the same amount of dimethyl polysulfide.