With the rebound, which is what I'm assuming you are talking about in regards to the treat placement, unless you are planning on teaching him to catch a disc with it? A vault is where they use your body to jump up to catch something, a rebound/fakey is where they just jump off your body. You want it fluid before you move to the wall that's for sure. Clean? I would have to see it. Reward in your lap and then toss the treat to the ground for a few reps, then fade out the reward in your lap and only reward on the ground. He should start to jump up with the intentions of jumping off right away pretty soon and then it will become more fluid.
I'll break it down for a solid hop on my lap-reward-hop off-reward for now. Thanks!