Sync custom titles with voiceover

Hi,I would like subtitles with custom formatting and have those synced to an mp3 voiceover.I'm using "custom titles" because if I understand corrrect that's how to apply custom formatting to the subtitles.
I've always been manually synching each sentence to each custom title but was wondering if there's a smarter method?

Have the video transcoded into closed-captioning file, use that to create sub-titles.

Hi Ben, thanks for your reply.
The caption formats don't allow me to enlarge them enough so a 90-year old one-eyed pirate can still read them on his mobile phone.
Is there any way to select all the captions on the timeline and do something clever to transform or copy them into custom titles?