The general rule is 1.5 times the max result for the dice for each step rounded down if there is no dice that fits.
D4-->d6-->would be d9 but there is no D9 so it goes to D8-->2D6-->3D6
The only oddity is that they seem to use 2D6 instead of a D12 for a max result of 12.
I have found that a single high CR creatures does not make for a very interesting or challenging encounter. Lots of PFS scenarios end with an encounter like this which ends up being very anti-climactic. The main reason is how the action economy works. Say you have a party of 4 characters at...
That's what was being played. There was only one venue with any game being played that I could make it to on my days off. Pathfinder Society was what was being played so I played that. That's pretty much all there is to it.