Removing the old paint “edges”

before you go ruining what you already have, why don't you try a few light coats of clear on some easily redoable panel, to see if you can find something compatible with what you already have. it looks great what you have done, maybe you can just clear over it and then you can wet sand or buff the clear coat.
IMO his best route is to stop and get a baseline on what he already has on the car before adding more that may react poorly to what’s already on there.
He’s already had to re-do too much, no need to add to it with maybes.

More than likely he should be able to let what he has FULLY CURE, scuff (grey scotch brite) and use a sealer primer over it followed by a proper SS or BC.

Almost 30 years in paint and body/restoration... I’ve gotten myself into and out of almost every situation you can imagine.
Take your time, read, study and learn from mistakes... this is how we learn.

Doing paint and body work the right way is not as easy as everyone will tell you it is, this is why it is the most time consuming and expensive part of a restoration.

Let us see the tag on the can of paint you used. Take a picture of it.