I don't know that it's possible to contaminate non-porous shot with LoS. Just rinse well and you're fine - hats part of the reason for soap and burnishing compounds. They keep particles suspended in solution which makes them less likely to stick to other stuff. I've been using the same stainless shot for two years with no trouble and no cleaning. This is how it should be.
The porcelain will gently "rub" the patina into the metal. Steel will take the patina right off and bring it back up to bright, pink copper. I don't know if it's because of the weight, hardness, or both.
I use the same barel for everything.
Andrea Robinson Silversmith, Gemologist, Motorcyclist, and Espresso Enthusiast MmeMagpie.com
I've found with LOS that steel shot doesn't move it... I;ve tried to remove LOS when I've got it darker than I wanted and I can't find anyway of removing other than sanding, filing or possibly sandblasting.....