You need to take your photography hat off for a bit and put your training hat on. You've been to school - you know what's needed to successfully teach someone something.
They need to understand first the value of learning - why do they need this knowledge? What's in it for them? (WIFM)
BTW - they need to trust that you're the right person for this as well.
So let's assume that you've established trust and credibitlity and successfully communicated the "WIFM". Now you have to teach.
Hands on learning works best, and it's also best if you have training scenarios. As has been suggested, I think it's best to have them watch someone else do what they need to do, and then emulate that behavior in a trial run. You can then further advise where they are deficient.
Boom, now they have a skill that you can leverage.
As you can't be there physically to teach - you need to provide resources that take your place. A video is a great resource for this. You might also explore supplementing this with a training manual.
As for being on the web, this is for business, no? Hire a model/actor. No one is saying you have to be the one to act - but you should produce a resource that can be used by your target audience. There's additional privacy that you could leverage within hosting platforms. YouTube, Vimeo, Wistia, Brightcove, Vidyard...the list goes on. You're not the first to request private access to content - so the solutions are already there.