Text Tutorial by Danixer.
1. Add any gun you want the item on public match.
2. Do the Custom Games UI Stack Glitch ( 1 controller , PS4 / Xbox One )
3. Friend will take you to custom games.
4. Find your weapon (you have item on) which you want to transfer to ( step 1 )
5. Press triangle on the item to personalize
6. Tell friend to go to public match
7. Press A or X
8. Close Application to save.
If you don't understand here is a video on it.