Arctic Alumina Thermal Epoxy would be the preferred method, but that will stick them on permanently. It can be "cut" with the addition of thermal grease to make it easier to remove in future.
Crazy glue itself is so thin that it usually works okay to just use that, especially if it's just on an epoxy package not a metal topped package.
Also epoxies designed for high thermal tolerance have fillers that make them more thermally conductive than regular epoxy, so using a very thin smear of those, such as the commonly available JB Weld works good too. However, when I say thin, I mean thin, a transparent smear.
Any thermal interface works best applied as thinly as possible. It conducts heat better than air, but not as good as the heatsink, so always use the absolute minimum possible. Thermal pads usually fair poorly for this reason, they are too thick. Thermal tapes can be iffy, and are best avoided on anything but epoxy/plastic cases to heatsink interfaces. I beleive plain crazy glue and thin JB Weld applications have been shown to be superior to many thermal tapes.
Edit: BTW to remove stuck on sinks, such as the one on your GF card, there are two methods. Either heat with a heat gun and twist off, works best for thermal pads or thermal tape, or if epoxy, place in the bottom of the freezer for a couple of hours (makes it brittle) then twist off. Twisting is preferred as it is less likely to unseat the chip.
Edit2: another possibility is the type of electrically conductive epoxy sold to repair heated rear windows on cars. It's not as common as the conductive paint type, but have seen and used it. That works rather well as a thermal interface because it is silver filled. Again, use a very thin smear.
