Ok i know this works because I tried it last night. Here is the setup.
You need a pty of SMN 6 of them. You need one of those SMN's to be lvl 10 or 20.
IF LVL 10 go to Buburimu Peninsula.
If LVL 20 go to Lower Delkfutt's Tower.
Ok now you need to have a kiter you can either use 1 of the SNM in your pty have him drop and kite or ask a friend. Last night we had a PLD friend kite for us.
So what you are going to do is LEVEL synth except for the kiter or friend. Have that kiter link 50-60 mobs at once. It takes about 10 mins. Once he has that much he returns to your pty. Then you have 3 smn Time Astral Flow the mobs.
Here is the numbers ^^:
60 MOBS dead at 300 exp each plus chain bonuses = minimum 18kexp
Now seeming you brought 6 smns you can do this 2 times ^^.
I diddnt believe it myself till i tried it.