Soda will work fine. A skilled blaster working with a propper soda set up (no disresepect meant, but this doesnt include the £100 ebay special blasting pots, they just dont allow the fine tuning you need for delicate stuff. A decent soad pot will run to about £5k) can strip paint from just about any material without damaging the base coat. They say that a good operator can take the top coat off the paint and leave the primer behind undamaged, im not quite sure about that, but theyre certainly very good.