At the company I recently joined, development for the product I'm now working on is done in a home-grown language with no applicability beyond this product team.

We're going to be advertising for new developers shortly, but I expect that this will take a long time because of the language.

Clearly, there will still be significant opportunities for our new hires to develop transferable skills alongside the specific language and business domain, but what can we do to make the roles more likely to attract candidates with a few languages under their belts already who are both willing to learn and capable of learning a new language quickly?