I've not done that but I'd try using a script (assuming the various styles have the same names in each drawing).
This is the result of using the command line "-style" command -
Code:
Command: -style
Enter name of text style or [?] <Notes>:
Existing style. Full font name = Arial
Specify full font name or font filename (TTF or SHX) <ARIAL.TTF>:
Specify height of text or [Annotative] <3.0000>:
Specify width factor <1.0000>:
Specify obliquing angle <0.00>:
Display text backwards? [Yes/No] <No>:
Display text upside-down? [Yes/No] <No>:
"Notes" is now the current text style.
Repeat for each style.