Judy,
The first 10 days or so it sat with the underside soaking in kerosene. It didn't touch the old crud. After that I used some solvent with old tooth brushes then went to cotton balls, then in the end to denatured alcohol and q-tips. She's still a grungy looking old lady, but not because of the crud. She's just been used a lot in her almost 100 years of service.
During all this I was also doing other machines and sewing projects as well, so I wasn't cleaning 24-7 on this thing. Felt like it though.
Joe