If I understand you correctly, you have a print passage that contains multiple typeforms for the same text. I direct you to The Rules of Unified English Braille Third Edition, 2024 9.8.1. 

The example beginning with the bank’s dictum: …  shows that an entire passage is italicized with three Bold Italic Words.  I hope this helps.

If you have a concern regarding (BF 9.2.3b), I would suggest posting in the Braille Formats Forum.