How much do you give, and how often can it be safely given?
It does depend on the strength of formula you got. Typically the baby one is 20mg/ml and you can give 1-2mls. You can give adult gel caps but just adjust the amout you give. The guidelines in using it is give a dose once every hour for the first 3hrs. Then you can continue to giive a dose every 3-8hrs after the intitial 3 doses.
How long does it typically take to take effect?
That really depends. On the bunny and their sensitivities. Also if gas is actually the problem. I've given it when I suspect gas but can't always be sure. I have also seen a result in half and hour same as FluffyBunny when gas was the culprit. With gas I massage the abdomen and use simethicone.
How do you administer it? Can it be squirted on a carrot or something, if the bun is still eating?
If your rabbit is still eating, they probably haven't got a problem. : ) Using the dosing syringe is really the only way you can be sure they get it.
Is it difficult to overdose? I can imagine with the dropper, that just getting one drop in the mouth or something would be difficult. If you give too much, will it be an issue?
As FB has already mentioned, it's difficult to overdose them. It works mechanically by breaking down surface of gas bubbles. It's not absorbed into the intestine.
I usually put the syringe in the gap between their front teeth and molars. Just be sure not to point it down the throat as they could aspirate any liquid given that way.
In this article there is a paragraph about simethicone under the sub-heading "I: Mechanical Treatments" http://www.bio.miami.edu/hare/ileus.html
Most Simethicone is flavored
FB, what flavour(s) can you get it in? Ive only found one brand here in Australia and it doesn't seem to be flavoured.