Not sure what you're talking about referring to shuttle busses at Zion. You don't mean that you must be on a shuttle to visit Zion, do you? Did something change since I was there in June on my Harley?
To access the road up to the start of the slot canyon you need to use the shuttle bus. This is the most visited area of Zion and was bumper-to-bumper traffic before they started the shuttles. At one time, there was a campground at the turn-around but had to be closed due to over-use which was destroying the beauty of the area.
If you want to enjoy the solitude of Zion, go to the north end of the park which most folks doesn't even know exist.
