On Rain's blog, he mentions cleaning the Singer 201 bobbin case, hook and race with rubbing alcohol. I did that, and just decided to do the same on the 66.
It took me around four hours because of stopping to photograph the steps. Plus, the wick didn't want to come out of the screw; so, I had to soak that numerous times.
My one machine without wick is from 1907, and the one with wick is from 1914.