I did some research on this and found a website that suggests teaching long division using "Double Division." I'm not a math teacher so I don' t know if this method would help an adult or not. However, it appears that some people who are having trouble with long division, understand this method better. I wonder if anyone has tried this technique.
As the old saying goes--"practice makes perfect"-- so I found several resources for long division worksheets which may provide added practice for your student. Sometimes repetition helps an adult comprehend the problem.
Although some of these websites are written for children, the suggestions may be helpful with adults as well. I'd be interested in knowing if any of these resources prove useful in helping your adult learn long division.