As you seem to be new to this,
1) axe the rotary buffer and get DA polisher. rotary buffers can do some real good damage if you're not a pro. Aka it'll look worse than you started. A DA polisher is just as effective and it effectively removes that danger due to the nature of how the DA...
FWIW I'm no pro but I have a full front XPEL Ultimate wrap on my Model S and I had no issues decontaminating , polishing, and coating over the film. I didn't even bother to wrap the film edges. I just did what I would normally do for a full 2 step correction. Aka citrus wash, Decontaminated...
If you don't have swirls than a 2 step polish is overkill IMO.
I would: Citrus wash, nanoskin autoscrub to get all the embedded gunk off (easier than clay bar and must be done before polishing), then use HD Polish (or HD Adapt) on a DA polisher with a white pad.
Then you can put whatever...