Information is available, but that doesn't mean it must be top secret. They can all be downloaded from the Internet. Whether to apply for the class depends on how many points you require. If the requirements are lower, such as below 80, I don't think it is necessary to apply for classes. I can achieve it by my own efforts. If the requirements are very high, you'd better sign up for a training class. Many training institutions may teach practical answering skills instead of improving their own strength. After all, it is not enough to rely solely on the strength of TOEFL, but also some answering skills are needed.

Strong English ability, and then willing to endure hardships and work hard, you don't have to report to class ~ expensive! Go to English forums and do more questions! Wish you success!