You have to stay in the graveyard shift even on weekends. It won't work trying to change on weekends. If you choose to work through the night, you'll need to live that schedule 7 days a week.
If you are sleeping immediately after your shift, you might need to allow about an hour to relax or settle a bit before attempting sleep. I always allowed myself to get a hot shower before going to bed. Helped me relax.
Don't drink any caffeinated beverages the last 4-5 hours of your shift. Don't drink/eat anything the last 2 hours before you plan to go to bed. It all interferes with sleep.
I had sound/light-cancelling window treatments in my bedroom and used a sound machine with nature sounds, not music. Music tends to engage your mind rather most of the time.
The ear plugs, I tried and did not like. Dark mask, I tried and did not like. I sure did not want to take any drugs just to get sleep.
You might have to have a few rough days/nights to get into it. Don't nap. Only sleep when you're supposed to.
Not everyone is cut out for it. And it is damaging to the body. I remember seeing a news documentary on the effects of 3rd shift on heart disease being as significant as smoking a pack a day.