For many years, I taught English in addition to Latin. One day, desperate to enact a quick turn around of essays, I edited 20 essays in 40 minutes while the students read the novel we were studying. I repeated this feat this four times that day and I was proud that everyone leaving the room had a thoroughly proofread essay to take home and revise. I corrected everything: comma splices, capitalization, run-on sentences, as well as issues with style and structure. I was, at that time, a very efficient editor. The problem was that my students were not. Since I was doing the editing rather than teaching editing skills, my students ability to edit improved very little.
I had an A-ha! moment when I attended a writing conference in which the speaker suggested that to be a successful writing teacher, you should train students to edit as well as write. To teach editing, the speaker suggested, you need to teach students what questions they should ask of their own paper. These may be grammatical questions such as, "Do I have a list of items? Are the items separated by commas? " or stylistic questions such as, "Does every paragraph have a topic sentence? Of course you need to teach students how to use grammatical tools, but once the skill has been taught, the question rather than the answer should be provided to keep students accountable for their own editing. The questions are asked on a separate piece of paper that you create called a "proofing paper" which guides students to check for the kind of errors that you know they can identify and correct.
What this also means is that the questions you require students to ask students of their own work should be limited in scope to the things they can reasonably be held accountable to fix. Subsequently, there will be a number of errors in grammar or in style that you need to just ignore. For some teachers, this was difficult. For me, it was easy. Bleeding red all over the page had done nothing to improve anyone's writing so I was happy to let it go.
This philosophy applies to teaching writing in Latin. If you give a writing assignment, decide ahead of time what grammatical constructions you want students to be held accountable to form correctly and ignore those they cannot do. For example, in my "Latin Silent Movie Project," students are held accountable to do the three things well that we have been practicing - putting nominative and accusative endings on nouns depending on the context and adding t vs nt to the verb. Prepositional phrases tend to show up in these scripts. Some are correct and some are not correct. I leave them alone.
Now because I want the students to correctly form nominative and accusative nouns as well as singular and plural verbs (third person only), I do not correct their papers of those mistakes. Instead, I had out a proofing sheet, that leads students through the questions they should ask themselves to find their own mistakes. Everyone reads their own script with one of these proofing sheets and then reads a classmates.
Students will ask you as they continue to ask me, "Will you correct my paper?" I tell them gently that I will not correct their paper because the point of this assignment is to see how well they have corrected their own paper. I assure them that if they have thoroughly proofed their paper according to the guidelines of the proofing sheet that they will do well. Students, particularly those anxious about grades, have difficulty believing this at first. They have been surprised before in other classes where they have been held accountable for too many mistakes they didn't have any idea they were making.
I tell them that I will answer questions that they may have about how to put on the correct endings and when to use them. In general, students ask a few questions in the beginning of the project - Is this right? and then write the rest themselves.
So to summarize - teach editing - not writing and free yourself from the burden of marking up multiple drafts and free the students from the tedious process of navigating points of red pustules to be rewritten. (Hmm... too much? Perhaps that line could use another edit.)