Okay, bear with me on this. I don't have hipshot's awesome pic to help.
I have an arty battery with a 6 grazing range. It is upslope of a gentle slope that is 2 hexes away. It is firing downslope at a target(C) 6 hexes away. 2 enemy units (A and B) are between the battery and the gentle downslope along the grazing LOF to the 6 hex target. Can the arty battery fire at the distant target and get grazing fire on the 2 closer units in LOF?
Or is arty fire either normal or grazing? So, if I wanted to shoot grazing fire I would have to target the furthest unit before the gentle downslope (Unit B)?
I guess I don't understand what grazing fire represents. Cannonballs bouncing through the ranks?
Grazing fire represents the apex of the trajectory not going above 2m, so along the line of fire it would be effective the entire distance, to include the bounce.
The slope negates the grazing fire effect. So in the example you could hit the 2 enemy units (A and B) before the slope, but not the distant unit.
On level ground you can hit all units in the line of fire within the grazing range OR fire a one hex at a longer distance. The longer range is hit by elevating the muzzle of the cannon. This then sends the ball over the intervening hexes.