Car finishes consist of multiple layers, so losing or gaining some paint might not be as bad because it seems.
If the paint is lost, the best hope is really a mild abrasive polishing wax such as Scratch Out by Kit. Be careful to never increase the damage by removing more finish. The objective would be to smooth the scrape and add layers of wax to cover up and protect.
The better situation is when paint is gained. Your good finish is probably just hidden. The offending paint or similar material can come off but this must be done gently. Do not try to pay it with touch up bottle paint until looking to remove the foreign paint first.
To scrape the transferred paint without damaging the underlying and adjacent finish, a solid yet flexible and tool is required. Metal is out of the question! Sandpaper may be the wrong choice. A metal putty knife, despite having an edge worn smooth from use is not a good option. A worn and polished plastic putty knife or kitchen spatula is preferred. Or for max control and safety, try your thumb nail!
Yes, you have perfect flexible, not abrasive scrapers on each hand. These keratin tools are created to be used and worn away. Now can be your chance to return to your aboriginal roots.
Gently scrape off the maximum amount of foreign paint as possible, then utilize a micro-polisher like Kit Scratch Out to finish the job and remove/cover smaller scratches and abrasions.
For areas cut completely from the finish, touch up paint will be the only option. Apply as little as you can and only for the affected area.
I cannot say the final results will look like new, however you will probably be alone who notices or cares. The other option may be the body shop. Be prepared to spend $$$ or get shoddy work meaning all the paint is going to be peeling off your bumper with the car wash the coming year.