i have only used super glue gel or duro brand instant gel.. they both work well.. you want gel and not just liquid because the gel will stay in place longer than the liquid.
like unknown said you want to stick the toothpick all the way through the stalk then you put the rubber band near the end of the toothpick on one side bring the rubber band under the rock to the other side and place it at the other end of the toothpick.. you want to make sure the rubber band is a snug fit to make sure it keeps the coral in place..
you can use super glue gel on various soft corals also, it really depends what you are fragging. that also applies on hard corals, it really depends of what you are fragging. some branching corals you just cut off a branch near the base of the coral ( candycanes, frogspawn ). hope this helped