DM Trailer Glitch Steps… at least, how I do it.
1. Eat a peyote plant near Del Pero Beach to unlock a bird in Director Mode & save game through phone (only required one time).
2. Join an Invite Only session with the character slot you want to use the DM Trailer with.
3. Enter a non-weaponized vehicle and locate the Time Trial on your map (changes weekly; ensure Time Trial is set to Show in your Hide Options – Other in the Interaction Menu).
4. Set to Last Location in the Interaction Menu and start the Time Trial by driving into it and pressing right on your dpad.
5. Exit to Story Mode through the online menu
6. Open Story Mode Interaction Menu and enter Director Mode.
7. Click Actors – Animals – and shortlist any bird.
8. Click Actors – Online Characters – and shortlist your GTA Online Character.
9. Go back to Shortlist and begin scrolling back and forth between the bird and your online character. This will duplicate the bird.
10. After 20-25 minutes of duplicating the bird, your character will move to the hay.
11. Once your character is on the hay but the bird is selected, remove the bird from your shortlist.
12. Click Actors – Beach Bum – and begin pressing square. This will begin to show you randomized DM Trailer outfits.
13. To bring one of these outfits online, they must have a Christmas Mask and NO blacklisted/invisible/festive components.
14. Once you’ve found an outfit you want to bring online, press to shortlist the actor.
15. Scroll back to Shortlist and select the outfit to enter Director Mode and ensure you see no blacklisted/invisible/festive components.
16. From Director Mode, Exit to Story Mode, force a game save by blowing yourself up or dying and then join an Invite Only Session.
17. If everything was done correctly, you should spawn with the shortlisted outfit on your GTA Online Character and can save this outfit.
There are a lot more tips & tricks to this glitch and so much you can do with it but this is the basic. If you can get this down, you can try more. Boca has great videos & a playlist.