My grandpa swore by mayonnaise for water rings on wood. It sounds crazy but it actually works.

Read somewhere that putting the carrier on the floor works because it's a more stable surface. Less sway and vibration than a seat, especially in a moving car. My friend's dog used to shake in his crate on the backseat, but putting it in the footwell stopped the whining. Might be the same idea with your cat, less motion sickness.

Stick with the stones. That electric stuff just grinds away too much metal. We use a two-sided diamond plate for a quick fix between full sharpenings on the water stones. Lets us get a working edge back in under a minute without wrecking the blade. For real volume, you just can't beat a practiced hand on a good whetstone.