Talk politics.

I don't understand why you couldn't teach this via apprenticeship, either. The complaint is that they have a lot of older guys who know this, but will be retiring soon. So why not do an apprenticeship and have them teach it directly? It makes a certain sense for the company (as it gives the worker only those skills specific to your company's product, and no certifications, meaning that it's less transferable and thus the worker can't leave as easily) and some sense for the worker (get paid to learn the skills rather than paying to learn them).