When writing end comments, don't actually write them by hand onto each student's paper. Instead, create a document on your laptop containing the end comments for each student. Start each student's end comments on a new page. Advantages:
If students submit their papers as electronic Word documents, use Word's "Track Changes" feature to type in margin comments. Another option when you have an electronic copy is to insert your comments directly into the text but highlight them in a different color.
If you find yourself making the same small-scale comments repeatedly (for example, if your student writes "try and" instead of "try to"), consider making a list of your usage rules, numbering them, and giving the students a copy. That way, when a student makes one of these errors, you don't have to write that "'try' takes the infinitive"; instead you can just write "rule 14." Include your own pet peeves in the list. In the list of rules you hand out, you'll probably want to include some elaboration with each rule, but you should make yourself a numbered list of the rules without the elaborations so that it's easy for you to look up each rule number.