I have also done a lot of homework in this respect.
There are many popular teachers in the market, such as long and difficult sentences, long and difficult sentences, Tang Chi, Zhu Wei and so on.
I used teacher Jing Tian's in New Oriental. I think what the teacher said is very good. No nonsense. It is full of work, and it is clear and easy to understand, so that you can get to the point. There is nothing else to spare. It is worth listening to.