To me trap is something of a gimmic. I've shot it a bunch, competed some, and just don't care for the nature of the beast. Part of the reason is exactly the issue you noted. The sight picture is unnatural in skeet. The target is rising and without a specialized trap gun, you will "blot out" the target when it is going straight away. Serious shooters overcome this issue with special guns that have raised ribs and high cheek pieces. Neither ever appealed to me, but I shoot because I want to be a better hunter. Skeet and sporting clays provide more variance and more realistic skills to work on.
To explain any type of sight picture is somewhat difficult. When I taught my wife I would say something like, "Well aim 3 feet in front" and she would look at me and say, "how do I know what 3 feet looks like?". My only answer is to shoot a bunch. Shoot with someone who can watch you, stand behind you, and explain where your shot is going.
A very quick tip: If you are ready with the gun mounted, and you find the target quickly, you should pull up to the target, pull over the target such that you can't see it, and squeeze, in one fluid motion. That target is rising and 90% of beginner misses that are on the target quickly, are because they are below or behind. Find it, swing through it, pull.