This is an experienced TEFL teacher. SO, I am a new member to this forum, but not unfamiliar to the world of TEFL, at all.

Here is my question: How do you go, as an EFL teacher, about improving the writing skills of your TEFL college students with low language proficiency whose writing products are still flooded in many, many grammatical obstacles?
Generally developing good writing skills involves learning to edit and revise constantly. Get your students to write short paragraphs on various topics then to ask other students to correct them. Once the student corrections have been made the students should re-write the paragraphs again and then have them proofed by a teacher, with the common mistakes discussed in class. This way the students learn the common mistakes and learn to edit and recognise mistakes.
Reading is also and important part of writing. The more someone reads the better their writing becomes.