1. You don't need to clean the chrome off if using compression fittings. However, I'd substitute copper olives for brass ones if brass supplied.
2. If you did want to use compression fittings and clean the chrome off, use an abrasive strip like Screwfix 2843K then "polish" with a scouring pad type material like Rothenberger Rovlies.
3. I'd use the same method for soldering, where you have to clean the chrome off, but leave out the polishing stage.