Remington Gun Club 7.5, 1oz along with the same in the Rio brand are you friend.
As far as score it will depend on the course set at the time. Some are hunter friendly and others for competition. You will know after a couple of rounds. Some places have both easy and hard stations, that are determined by where they place the stand in relationship to the trap.
So it sounds like if you're just shooting to keep the rust off a guy would err on the side of a tighter choke?
I love competing and gaming games but I doubt see this being a sport I ever get into seriously. Just something for my son and I to do every other month or so.
We just plan on using our regular bird guns in 20 gauge.