so encourage process rather than drawing attention to surface errors, such as article (a, an, the) use.
Encourage critical thinking and writing-as-process by asking questions about sources and evidence through writing and other communicative activities that contextualize and encourage students’ opinions.
Encourage students to discuss their writing and your critique of it with you during office hours.
Disabuse students of the idea that writing well is only about grammar by providing comments on the context of their argument and content.
Discussions about content will naturally lead to grammatical corrections as students struggle to find clear ways to express their ideas; over time, simply through exposure, students’ grammar is likely improving.