In the most recent encounter with the couple, the husband mentioned to my husband that his daughter needs a darkroom set up. She could 'sure use the help.' There's that word again!
Since you live somewhere in central NC, I have a suggestion. The next time they ask--send them to either Southeastern Camera or Peace Camera in Raleigh. Both stores have darkroom supplies and people on staff who could help them. the more darkroom business we send to these stores in our area, the better we'll be in the longrun for getting supplies ourselves.
I have taken time out to show people how to set up darkrooms, or to help students out. I don't really have a problem with that, but then again, I'm not a photo teacher. I don't help people out by shooting stuff for them, because I'm a photographer, and when I'm not working, I don't want to be working for free, if that makes any sense? I brush these sorts of inquiries off pretty fast. I've blown off so much side work, it's not even funny probably to anyone who freelances, but I'm just not interested, when 75% of the time, the reason why they ask, is because they don't want to pay a living wage. This is a generalization, of course, but like Jonathan Brewer says above--it's a manipulative ploy often, and you can tell.
So I'm pretty upfront with them, and just say, sorry I'm not interested. It's helpful to think about it this way--when people approach you, it's not like you are bidding on a job, or making a cold call. They're asking you to do something. If you're not interested, but they persist--then it's their problem. For me, when this happens, it's usually somebody wanting me to shoot something. If they persist---what I do is give them my "nuisance fee" which is high bid. really high. you can gauge it by your interactions with them. if you think, well, it might not be that bad, but it would take this amount--then see if they're interested. If they turn out to be the clients from hell, the kind everyone has had to deal with--then the nuisance fee can be pretty high. you just bid yourself out of the ballpark. it's like self-preservation. life's too short to spend your off-time dealing with difficult people.
but seriously--send them to a camera store. we have some good ones in the triangle that are still stocking used darkroom stuff and supplies.