I often use thick gap-filling AC, but I usually work with LEDs, so no heat issues like with bulbs.
If it's a plastic ceiling, you may not want them directly on the ceiling because of that. Instead wire and attach them to a suitable piece of stripwood stock. Glue that assembly to the ceiling so there's some stand-offf. Even though small, bulbs get hot enough, depending on your input voltage, to melt things or at least warp them over time.
Mike Lehman
Urbana, IL
I've used a hot glue gun in the past with success. Just be careful not to touch the tip of the gun to the wires, you will melt the insulation. Someone told me about that, yeah that's it.
how do you attach grain of wheat lights on the ceiling in a building