The spirals on Foster and Brenneke slugs do not actually impart any spin onto the projectile, they're just a gimmick. If you want 1-3 MOA precision from a slug you'll need to get a rifled barrel and Sabot slugs or get lucky with a high quality (Carlson, for example) rifled choke.
What really defines a Foster slug is the hollow base, the expanding skirt works in principle similarly to the Minie Ball. Brenneke Slugs will have a solid base.
Either way, these are not Sabot slugs and whether Traditional, Brenneke or Foster they're safe to fire out of basically any modern shotgun.