What color vehicle, how significant are the swirls? Your statement about LL claims of removing swirls didn't sound like the LL product I'm familiar with, so I grabbed my bottle. No claims of swirl removal - oxidation, tar, bird stains, bug marks, road grime, and grease - yes.
Try the Scratch X on a small section, you've already got it. Try the NXT many have reported good defect hiding with the NXT, I haven't personally witnessed that.
You may have to order some SMR from an online source if the above tactics don't work.
I think that LL will not be compatible as a topper with the NXT, but as I've said I haven't used LL as a topper. Dale may have some experience with that. I'll defer to him or anyone else who has used it in that manner.