Just ask them how much they'd be willing to pay out of their own pockets in the form of higher taxes so that we can accomplish the mission, withdraw and leave Iraq behind as a stable nation.
War hawks also tend to be in the "we don't want to pay no stinking taxes" crowd. Asking the question points out the inherent disconnect they have regarding supporting the war and funding the war.
The only problem I found is that they won't answer. Hopefully, by asking the question it at least gets the pinheads thinking about what it will cost them.