This macro will help you standardise your document's hanging indents AND makes use of styles. It will greatly reduce inconsistency in your styling of the document because it is resetting the paragraph formats and removes local paragraph overrides.
Code:
Sub AllStylesSetHanging()
Dim aStyle As Style
For Each aStyle In ActiveDocument.Styles
If aStyle.Type = wdStyleTypeParagraph Then
If aStyle.ParagraphFormat.FirstLineIndent < 0 Then
aStyle.ParagraphFormat.FirstLineIndent = -CentimetersToPoints(1)
If aStyle.ParagraphFormat.LeftIndent < CentimetersToPoints(1) Then
aStyle.ParagraphFormat.LeftIndent = CentimetersToPoints(1)
End If
End If
End If
Next aStyle
ActiveDocument.Range.ParagraphFormat.Reset
End Sub
Whilst we could choose to write the macro differently to deal with local settings on every paragraph, that macro would run very slowly and result in a poorly formatted file which is why you have had pushback on your asked-for approach.
If you see other non-hanging paragraphs change as a result of this macro, you should apply the right styles to those paragraphs.