People say it's best to email professors in universities you are applying to.
Anyway, to email a professor, I think I need to read at least one of his/her papers, study it and write a remark, which definitely takes a lot of time. On the other hand, it is normal for a student to apply for Ph.D in many universities. So my question is, do people usually email one professor of each university?
From my perspective, it would be impossible to do such a task. But I want to hear others' opinion on this matter.
Thank you in advance