Letter-for-letter spellings are common in proceedings. Hyphenate letter-for-letter spellings. Here are a few things to remember.
The hyphen is always attached to the letter that comes after the hyphen.
...It's spelled V-o-l-d-e-m-o-r-t.
…Dumbledore? D-u-m-b-l-e with a -d-o-r-e?
…Okay. And is that with an -o-o-r or -o-r-e?
When capital, lowercase or double is interjected before a letter, precede it with a comma & no hyphen, use no punctuation between that word and the letter it refers to, and continue.
…McGonagall, M, lowercase c, capital G-o-n-a-g-a, double l.
When a word is used as an example in a short phrase, it is separated by a comma and the word gets quoted. When spelling is interrupted, the last letter of the spelling before the interruption does not take a hyphen after it. Remember, the hyphen is attached to the letter after it. So when the spelling resumes after the interruption, the first letter will be preceded by a hyphen.
…Hermione, H-e-r-m, as in "muggle," -i-o-n-e.
…Is that Dumbledore, D-u-m-b-l-e, then "door," -d-o-o-r? Or is it -d-o-r-e?
...His name is Russell, R-u-s-e -- -s-s-e-l-l.
When a complete sentence is used as an example, set it off with dashes.
…McGonagall, M-c-G -- that’s a capital “G” -- -o-n-a-g-a-l-l.
The capitalization and spacing are just as they would be when the word is written normally. When a name comprises separate words, there is no hyphen in front of the spelling of the second word.
…McGonagall, M-c-G-o-n-a-g-a-l-l
…Rubeus Hagrid, R-u-b-e-u-s H-a-g-r-i-d
…De Santis, D-e S-a-n-t-i-s
…DeSantis, D-e-S-a-n-t-i-s
For reference, see LMEG 157, BGGP Hyphen.40–43, and margieholdscourt.com letter-for-letter spelling tag archive.