The Sheridan Center offers English Language Workshops. These can be found at: https://www.brown.edu/sheridan/programs-services/english-language-learning/english-language-workshops. Workshops include colloquial speaking, academic speaking, academic writing, and other topics at various levels. The Sheridan Center has an assistant director, Sara Gramley, who is available for individualized language support.
Brown Center for Language Studies offers English classes for non-native speakers to improve their skills so they can teach and do research. These classes are listed under EINT as the department. The specific classes are shown at: https://www.brown.edu/academics/language-studies/courses/eint. Lauren Clarke can help apply to get in to one of these classes. Successful applicants are interviewed to be placed in an appropriate class and section. The above resources are also summarized at: https://www.brown.edu/sheridan/programs-services/english-language-support.
Brown's Writing Center offers assistance with improving writing on an appointment basis. Appointments take some time to schedule and are limited in duration, so are often not enough for a typical research paper. Multiple appointments can be made, but lead time can be an issue. Some of the staff are more cognizant of issues international students may have, so it can be helpful to try to get an appointment with an appropriately trained staff member.
The University of Michigan self-directed writing questionaire may help to identify areas that might be limiting one's writing. To use this service, you will need to set up a friend account with UM.
There are some automated tools to help with simple writing issues, but they do not go much beyond checking spelling and a few grammar rules. These include Microsoft Word (make sure you have the language set correctly), Grammarly (available free on the web), and White Smoke.