My DH's views are also very clear. We have postal votes and he did the actual voting bit himself but I had to show him where to sign and did the, slightly complicated, folding and sealing then posted them.
As a Polling Agent for my Party, I have assisted several people to vote in the polling station booth when requested. They have included people who are blind, have special needs, learning disabilities, are illiterate, or have a shaking disease. I have never had a problem with ascertaining their wishes and helping them to vote.