Marzano and feedback

I really liked the chapter about the importance of feedback. I am not very good at providing feedback all the time. It takes so long to read, grade and write comments that I get overwhelmed and stop writing comments. One year, several years ago, I had my students write letters to me about what they were reading and then I wrote back to them-every single week. It took a long time to write those letters, but I enjoyed seeing their faces when my students read what I had written to them. Many suggestions I have read about suggest using rubrics for grading and comments. I am slightly confused how to use rubrics for feedback. If anyone has ideas how to implement this idea let me know!