Hi there. I put the probe in the potato to give me a reading of the smoker temp itself. Keeps it up off the grate and to give a more accurate temp. Some people use a small block of wood with a hole the size of the probe and use that, I just grabbed a tater and used it instead. As far as the meat goes, I put the other probe in the thickest part, when that piece comes to the temp I want, the rest is done as well. Some people who have really large smokers will have a few probes going at the same time as there can and often are differences in temperature thru out the smoker. Also, if one if doing say a brisket, a couple of chickens, a pork loin and a fattie, you are going to want a few probes to tell where each one stands as far as temps go.
The down pillows worked great. I was totally surprised by how long that brisket maintained its temp. Over 10 hours in the cooler with the pillows and it was still too hot to handle with bare hands.