Usually hard-of-hearing blind people or visually impaired (or practically deaf with different extent of vision loss who use hearing aids) are able to use oral speech and write properly. Among them you can meet people with inarticulate, deformed voice speech.
Deaf people (totally deaf or practically deaf) with different extent of vision loss (from total blindness to slightly remained vision) divide into two groups – those who speak and those who sign. There is no opportunity to use oral speech for communication with them.
Deaf people who speak can address you by voice (if it is normal), but can not receive voice feedback from you. With people who use sign language it’s harder to communicate even in one-way mode.
For proper communication with these categories of people you need to use services of special interpreters for deaf-blind people or sign language interpreters who know basics of communication with deaf-blind and their psychological peculiarities.