In the states in the midwest US that I have been in, funeral processions are part of the Rules of the Road. We have right of way through red lights, stop signs, and yeild signs. Headlights on.
If there are not enough flags for all of the cars, the first and last definitely have flags, and every second or third do.
I've been in a procession through a large city, which had ramps from the interstate that we had to pass. We still had right of way. The ramp drivers were not to merge.
We live a block from a large cemetery, so when we are working in the yard or having a glass of wine under the shade tree, we still stand and if there is a flag on the lead car (police officer, city official) we put our hands over our hearts. It's only happened a couple of times in 12 years, but it's what I learned to do in southern Illinois by watching others.