*Spoiler alert* He didn't gain fluency by just using the trainer.
Let's talk about what you will get out of it....
The Pronunciation Trainers contain the following bits and pieces:
- A set of 3-4 videos that walk you through the consonants, vowels and spelling rules of your target language
- A set of 400-800 flashcards (an Anki .apkg file) complete with sound files and images.
In the flashcards, you’ll start with spelling rules mixed with minimal pair tests. The goal of these flashcards is to train your ears to hear your target language’s sounds, and to train your eyes to recognize the spelling patterns that produce those sounds. If your language involves a non-Latin alphabet, then the cards will walk you through the letters in that alphabet as well, teaching you visual mnemonics along the way to help.
As you pick up spelling rules (and letters), you’ll also be asked to spell example words, so you can practice combining spelling rules into full words. Eventually, you’ll run out of spelling rules to learn, and then you’ll get ~80 more words to practice, and then you’ll be done.
You can start learning words whenever it feels comfortable to do so and you have enough spelling rules and sounds under your belt that they’re not totally overwhelming. The exact point will vary from person to person, but if I were to guess, I'd say you can comfortably start as early as 8-10 days in for languages without new alphabets and 13-15 days in for languages with new alphabets, if you’re going at the standard, 28 new cards/day rate.