It takes about a week to get the interface translated and to start collection, for any language with at least 5000 sentences in the public domain. I helped bootstrap Guarani and Breton and a few other languages spoken by friends of mine, but in the end, it just takes one or two people. I think in general there is a big difference in engagement if STT/ASR already exists for the language (e.g. Hebrew, Danish and Korean) and if it doesn't exist at all.