The Canvas process is documented here [1]. You can copy paste the name+email columns from an excel/googledoc/csv file into the textbox and it will work. It is not tedious at all.

Obviously, direct upload of excel/csv would work just as well or better, if they were clever enough to pick out the name and email columns from the others.

[1] https://community.canvaslms.com/t5/Instructor-Guide/How-do-I...