So far, so good. What I've done that has worked without being a boo-boo has been exactly what you are doing until it no longer registers heat. I found a digital oven thermometer. The one I have has a long cable from the sensor (inside the oven) to the counter where the digital thermometer is. I straightened the sensor, used electrical tape and taped it to an old arrow. I use this to monitor my temps in the compost pile. Stick down deep to the middle of the pile. When it is no longer higher than the ambient air temperature, it's a safe bet that it is ready for use.
Also, when i clean out the coop during the fall/winter, I take and put the droppings directly on the garden. They will age over the winter. I turn them under early spring and have not had a problem doing it this way either. I live in Tennessee, so the droppings that I turn under as well as any other organic matter, is long gone by the time I'm ready to plant. I cannot get over the improvement in my soil structure!