Only if you need it to stick. Heat sink compound is usually grease based, not a good thing for adhesion.
I got some "Artic silver - thermal adhesive" which is a two part epoxy. Worked well. Not sure where I bought it - may have been ebay.
you can only tell if it's conductive, you need a "megger" to find out what the dielectric strength is. that's important to know if you are applying more than 12 to 50 volts to devices on a heat sink.Theoretically, I should be able to test the electrical conductivity of any thermal grease with a multimeter, right?