I've used temperature sensors on parts before to determine soak progress. Our CMM came with a part sensor and it's sometimes a challenge to find the best location - usually underneath or on an inner vertical wall to avoid probe paths. Securing the sensor on non-ferrous parts involved a combination of all thread and coupling nuts to hold the sensor up or wedge it against something. I've found that TIM not only helps for non-flat cast surfaces but also helps keep the sensor on the part due to the "suckiness" (someone help me out here). Cleanup isn't bad. Not sure what ingredients are in the compound - you may need to assure it complies with your customer's parts requirements. I first tried some from home that came with a CPU cooler. Amazon & Ebay are good sources for bulk.
