I don't remember exactly but the basics steps are:
-Extract the m2/skin files (using wmv might be easy) and convert from cata format to 335 format. Be carefully with particles, if you don't convert it correctly the model can't work.
-Using other 335 spell that have a similar effect to wing spell, clone the spell and go to colum 131/132 (zero based). This row means the effect that spell will cast. You have to manually do this effect in SpellVisual.dbc. Also, SpellVisual.dbc is connected with SpellVisualKit.dbc, and SpellVisualKit.dbc is connected directly with SpellVisualEffectName.dbc. (Connected means that IDs that appears in Visual are taken from VisualKit, and IDs that are in VisualKit are taken from VisualEffectName).
To sum up:
-Extract from WMV the m2/skin wings files and convert to wotlk.
-Edit the DBC's:
Code:
-http://www.pxr.dk/wowdev/wiki/index.php?title=Spell.dbc
-http://www.pxr.dk/wowdev/wiki/index.php?title=SpellVisual.dbc
-http://www.pxr.dk/wowdev/wiki/index.php?title=SpellVisualKit.dbc
-http://www.pxr.dk/wowdev/wiki/index.php?title=SpellVisualEffectName.dbc that contains the m2's name
-Make a custom patch
-Put dbc's in dbc folder in your emu
If you have problems converting m2/skin files or editing DBCs feel free to answer and attach the files, I will try to help you.