ProfHacker’s section of the Chronicle of Higher Education has a few posts related to blog grading, such as

• grading student blogs;
• grading rubric;
• blog audit, and
• pre-class quizzes.

Also, Dr. Naomi Johnson and Dr. Heather Lettner-Rust have developed a blog rubric , which can be adapted across disciplines and student levels.

As for the process of grading, you may create a submit-by-url assignment in Canvas and grade each  student post/e-Portfolio privately.

Student view of the assignment:

Instructor’s view of a student blog post in Canvas Speedgrader: