Most of the time people just want to know "what's up?", so I have to do vague all the time.
I muse on it until the focal piece reveals itself. Usually it's the center of activity. Then the story unfolds around that.
There is much mediumship that comes into play. I wouldn't say I'm psychic, but my customers would say I am a medium, something I would not have said about myself before I started doing these kinds of readings. I think it brings it out in you.
Ted Andrews' book "animal-wise" is definitely a good one to have at hand if you wind up with a lot of creature bits. And you can google "dream interpretation <item>" while you're learning. I still do this for online readings if something screams "hey, there's something about me you don't know yet" and when I'm gifted a new piece that's unfamiliar.
I do read every piece, but I don't dump all 300 out on the mat. Just whatever comes up. If you are having to ignore pieces you probably have too many out. Alternately, those are pieces that mean nothing to you. Look them up and/or journal about them. If nothing ever comes to you, cull it and save it to seed someone else's oracle.
The first thing I do to kind of get into the swing of each reading is to list out the junk and its potential meanings in a column, noting reversals. Then I describe how it fell, what clusters are there, how any pieces interact with any others. By that time I usually know where to start and have a vague idea what the reading is about. Then I go into a little more detail about the pieces. Finally, I draw it all together and make any suggestions that seem appropriate. (I have a collection of standard speeches, LOL.)
As with the magic eye posters, you have to teach yourself to unfocus your normal vision and let the oracle's perspective reveal itself. That was a very good analogy! Each throw is a new picture made up of small, seemingly unrelated bits. You have to stop trying to see it and just let it come into focus on its own.