This link contains Excellent information regarding seizures and what to do....The information about putting an ice pack on their back is in there as well. It explains exactly where to place it.
When Miko has had seizures, I've used the ice pack on him, and it helps shorten the length of the seizure. Please read the whole thing.
Emergency Care For Canine Seizures - Epi Guardian Angels
The part about valium is not pertinent to dogs who are seizuring due to liver shunt. Dogs with liver shunt who are seizuring are usually given a lactulose enema initially. If the seizures are continuous, then they use other methods to get the seizures to stop. If it happens often, they are typically put on potassium bromide.