I don't know that you can completely avoid fat rendering, but I think you can minimize it.
I don't have any science behind what I do. But here's the logic I follow. I use a hot water bath after smoking, to finish cooking my summer sausage. Water is a more effective heat transfer medium than air, so a water bath reduces the cooking time. As a result, the water bath reduces the time that the sausage is exposed to heat. And, since it transfers heat better, I run my water bath at 160, to bring my sausage IT to 152 degrees. I always find fat residue on my turkey roaster insert after a water bath session. And there is the slightest film of grease on the casing. But, when you look at the sausage, there is no indication of a fat out problem. If you are cooking to a lower temp, I would think that you could use a lower water bath temp and reduce the risk of fat out.