Woo hoo! The residue is gone from two of the blocks that I worked on today. It was the lighter fluid that removed it all in just a few seconds. Then I used mild soap and rinsed the area in cold water. No discoloration, no odor from the lighter fluid, no residue. And the best part -- I didn't have to buy any product. When I told my hubby about the lighter fluid, he said "I think I have some in my workbench" -- and he did and it worked!!!
I have learned a lot from all the suggestions you've all shared on this issue. Thank you again - you're all a great bunch and tremendous resource!!!