Listen through once first. Know in advance where you are likely to stop
Do not use your voice yet. First, listen through once and get a sense of what it is about. Make a note of the places that felt fast, and the places where words linked together and sounded like a single lump. The reason is simple: if you chase after the audio without the content in your head, when you stop you cannot tell whether you failed to catch the sound or failed to understand the meaning.
You are not following a whole sentence. A short phrase is enough
A whole sentence at once is too ambitious. Start with a short stretch, up to a breath or a break in meaning. Layer your voice over the audio, following slightly behind it, and once you have said it through to the end, move on to the next part. If you get stuck, stop there. The very phrase where you were left behind is the place you should work on today.
When you stop, cut the section shorter before you slow the speed down
If you start over from the beginning, you will usually fall behind again at much the same word. So cut the section differently. Starting a little before the word where you began to lag, shorten it to a length you can say without straining. Once it is shorter, you can often keep up without touching the playback speed. Save slowing it down for when you still cannot ride the flow of the sound.
When you go back, too, there is no need to wander around hunting for the right number of seconds. If your audio can use phrase divisions, just go back to the previous phrase in Rehear. You can repeat the same place right away. If a division falls in the middle of a sound that is hard to say, use how to set the range you listen to with A-B repeat to decide the range yourself.
Listen → layer your voice over it, slightly behind → go back to the phrase where you stopped. Do not start over from the beginning. Resume from the section where you stopped.
Use the transcript only for the sounds you cannot make out
If you still catch on the same word even after shortening the section, the sounds have almost certainly linked together and are sounding like a different word. Stop your voice for a moment, open the transcript, and compare the sound you heard against the text. Automatic transcripts do make mistakes, though. If your material has an original text, treat that as the correct version.
Once you have checked, close the text. Follow the same phrase this time by sound alone. If you keep layering your voice on while looking at the text, your eyes, rather than your ears, will take the leading role. When to open the transcript changes depending on the purpose of the practice, but the basic rule is to open it only when you cannot make something out.
Once you can say it, it is only finished when you return to the longer flow
Do not be satisfied just because you could say it in a short section. Listen again, including the phrases before and after, and follow the sentence where you had stopped, continuing on from the sentence before it. You could say it when it was cut short, but in the flow you fall behind again. That happens a lot. When it does, shorten it once more, and once you can say it, widen it again. You build the skill through this back-and-forth.
If you can move into the next sentence without being left behind, that place is done. If you want to try the practice of stopping the audio and then saying a sentence back, next move on to how to do repeating.