Ok you can use IMG tool for Bully. Explanation Listen carfully! After you have download it go on to it and open up world in stream folder. Type in on find NDH3 it should go to Nerd clique skins if you go up or down you can find all other cliques like Bullies and Preppies ETC. Now extract the NIF and NFT folders of the skins to STREAM and rename them SP_(Outfit name of your changing) And the outfit might have like Example SP_Mascot SP_Mascot_B SP_Mascot_H
You rename first one SP_Mascot then copy it and paste it TWICE and rename first one SP_Mascot_B and second one SP_Mascot_H. Do that for both NIF and NFT files. After that you find the SP files on IMG tool and delete the SP_Mascot SP_Mascot_B SP Mascot_H (IF changing Mascot outfit!) and they have NIF and NFT files to so delete all of NIF and NFT files of the outfit you changing! Then press add on the toolbar (add is on commands) and select all the SP_Mascot ones and select add. Now last part!! select the ones you just added (should be at bottom of IMG) and on commands click REBUILD ARCHIVE now when it is done rebuilding archive go off IMG and go on Bully and wear the outfit you changed and you should be that skin!