An attractive alternative to the classic mica-washer-plus-grease is provided by greaseless silicone-based insulators that are loaded with a dispersion of thermally conductive compound, usually boron nitride or aluminum oxide. They're clean and dry, and easy to use; you don't get white slimy stuff all over your hands, your electronic device, and your clothes. You save lots of time. They have thermal resistances of about 0.2-0.4 degrees per watt, comparable to values with the messy method. Bergquist calls its product "Sil-Pad," Chomerics calls its "Cho-Therm," SPC calls it "Koolex," and Thermalloy calls its "Thermasil." We've been using these insulators, and we like them.