Do you have any advice for the person an OCD person is seeking reassurance from? Is it best to just say that seeking reassurance only strengthens the worries and you have to let it go instead? And once I've established that with him, I can simply say "let it go" a reminder to not seek reassurance.

The biggest problem for him is that his recent paranoia prevented him from doing many of the things he previously used as distractions----video games, listening to music, etc. At first that was a bad thing, but it has turned out to be a good thing because he started learning how to distract himself mentally without needing to be actively doing or listening to something.