First, the 1977 Textbooks Format Code was totally revised in 1997. The 1977 book that you refer to is obsolete and should not be used at all. The current rule book is Braille Formats: Principles of Print to Braille Transcription 1997. The BANA 2007 Update takes precedence over previous rules that it covers. The Update does not cover everything. Rules that the Update does NOT cover remain the same as they are now.
The rules for foreign language braille are found in the NBA Interim Manual for Foreign Language Braille Transcription, which is available only from the NBA national office. In general, foreign language rules folow Braille Formats. However, since there are many issues that occur in foreign language that do NOT occur in English, the foreign language rules take precedence over the equivalent rule, if any, in Formats.
The applicable rule in the CURRENT 1997 Formats rule (Rule 3, Sec. 4c(2) says NOT to insert hyphens not present in print. In foreign language braille, the rules for special typeface within words are found in the Interim Manual, Section 3.3.
It would be most helpful if you coudl supply the EXACT Spanish word or words you would like help with and to show exactly what letters with such words are emphasized. If you can scan and attach copy of the print page, that would help the most because it would show the context in which this is occurring.
I have tried to supply general information. If you can send some specific information about your issue, I'll try to provide answers that are more specific.
Hope to be of further service!