I too have used 303 on decals in the past as it keeps them from getting faded from UV exposure. However, I'm not sure what you're asking. If after you've removed the wax, then maybe you can use 303 regularly like I did. My decals looked brand new even ten years later.
Here's an interesting read that I've had bookmarked from a detailer that you might find interesting:
RV Decals