Might be known, but my friend came up with this yesterday. this is great for lvling in greater rift, you will not beable to upgrade your gems while doing this.
1. have a friend with trialkeys and you atleast one lvl 1 keystone. (lvl dosent matter aslong as its 1+)
2. everyone except the friend leaves the game
3. The friend starts a trial and teleports out instantly.
4. everoyne joins the game.
5. Go play grift from lvl 1 and always upgrade keystone. (the friend with keys is should upgrade gems when you cant complete an higher Grift)
6. Repeat.
We did this cause we had friends who didnt do any t6 rifts and didnt have keys. and did 1-11-21-31 repeat.
If you ever fail a grift the keystone will dissapear.
This is very good cause grift > t6 by far in xp atm since they go so much fast with pylons everywhere + % xp works.