Like Pat, I was also able to remove numbers from an mid 2000’s Lionel docksider using mineral spirits.
I have found Krylon semi flat black. #1613 to be a great match for postwar Lionel black. The only drawback is that it’s in their industrial line, not the consumer line. You can’t find it at hardware stores etc. I have had to get it online and usually get about 6 cans.