I second the above method of cooling the milk. I'd be wary of using powdered milk, though, because they often add milk solids to it and you don't really know how much lactose you are dealing with to begin with. Personally, when I make SCD yogurt, I use 100% half and half. But you should hunt around for half and half that consists solely of the following ingredients: milk (or whole milk) and cream.
Stay away from any half and half that has carageenan like the pague (most of it in the sotres does have carageenan). Carageenan, an undigestable gum concentrate extracted from seaweed, is actually used to induce colitis in research rats! I also stay away from other milk additives like phosphates. You can also make your own half and half by mixing whole milk and heavy cream in equal portions, but it is even harder to find half and half without carageenan.
I happen to incubate my yogurt for around 36 h and this seems to make it even better tolerated for me- presumably further lowering the lactose. I think beyond 36 h and you might start losing too many of the probiotics.
One more tip... I use a yogurmet yogurt maker with a hole drilled on top of the container so I can stick a cooking thermometer down into the container. I then plug the yogurt maker into a dimmer switch, which I purchased at Linen n Things for around $20, so as to adjust the electrical current to the yogurt maker to prevent overheating. Otherwise i find all yogurt makers just arbitrarily heat up the milk regardless iof room temp etc and it can heat to 120 or even 130 F as opposed to the recommended 105-110 F. I keep it rigorously in this range and I find this makes better quality yogurt. You can overheat the yogurt and still get good, thick yogurt, but I figure that the consumption of lactose and probiotic quality may have suffered from the overheating.
Sorry for getting so long winded- as you can see I am hard core when it comes to yogurt making!
Pancolitis dx'd 1986, full med-free remission 88-97
Flaring or simmering ever since
10 20 17.5 15 12.5 mg pred, 100 mg Imuran
Probiotics (Primal Defense and others), TSO
Turmeric/circumin, fish oil, many vits/minerals
Lower-carb version of Specific Carb Diet (SCD)