Your blind or visually-impaired student probably knows best what they need from an access assistant. You will save yourself a hassle and prevent frustration by allowing your student/researcher to conduct the interview and hiring process themselves. Furthermore, I believe it is very important to give the student the right to fire access assistants who are not effectively performing their responsibilities. Other blind students and I have had the experience of being assigned access assistants who are simply not suited for the job, or who do not take their work seriously. I have heard stories about students going to the disabilities office to complain and being effectively told, “This is what we’ve given you, take it or leave it.”
The purpose of access assistants is to give visually-impaired and blind students the same access to academic materials as sighted students. If the access assistant is not able to accomplish this (by lack of effort/investment, unreliability of schedule, lack of English fluency, etc.), a disabled student should be able to talk to the disabilities office, without the fear of appearing demanding or ungrateful, about hiring a replacement.
Disabilities offices have, despite good intentions, often purchased incorrect tools or arranged my workspace poorly because they didn’t permit me to play a role in the decision process. I’ve found it more convenient for everyone when the disabilities office has me tell them what I need instead of consulting with a third party.
During my first two years as a graduate student, the access assistants, instructors, and staff working with me would all meet together once a semester. We held these meetings at the end of the semester so that the instructors for the following semester could talk to instructors of the current semester. This allowed advice to be shared and progress to be built upon in a clean and orderly manner.
Meetings like these help educate an entire faculty on how to best educate visually-impaired students, rather than having each professor and student figure it out case-by-case. I would highly recommend holding meetings like these to improve and standardize support.