Just to chime in...
Most of the time when I see someone tell others how to remove paint transfer they recommend machine buffing the affected area.
My experience is this can lead to burning through the paint or "twisting" the paint in the process.
Why?
Because in most cases, when a fender or bumper, even door on your car has been rubbed against hard by some other object and had paint transferred onto your car's body panels the paint transferred is IMPACTED
incredibly hard onto the surface to the point that it is functionally now a part of the impacted paint.
Buffing to remove it will require time and when you only buff a SMALL area for extended time you heat up the surface and this is what leads to problems or like the saying goes,
turning a mole hill into a mountain.
Instead, the safe way it to go old school and abrade off the impacted paint by hand using a quality compound and either terry cloth or microfiber and the reason for cloth is you use the cloth as a form of abrasive to work with the abrasives in the compound.
The rubbing of a compound against the transferred paint will gently remove the transferred paint without creating heat to the rest of the underlying paint. (unless you have the muscle and hand speed of Superman).
This approach WILL likely leave marring on the underlying good paint but then all you do us use the normal protocol any of us would use to remove swirls, scratches, oxidation or water spots from paint and this will remove the marring. The normal protocol to clean up any marring would of course be using ANY orbital polisher with a quality compound or medium cut polish with a foam pad.
After removing the marring, then apply whatever you're using for an LSP.
LSP = Last Step Product
An LSP can be a traditional car wax, a synthetic paint sealant or a ceramic coating.
Hope this helps...