RE: Recommendations for Plastic Friendly Grease
Hi Streetsquid,
In answer to your question. There's no need to add lubricant of any nature to a "sealed bearing". It is by definition lubricated and sealed and will perform perfectly well in any application unless it's overheated. Sealed bearings will not overheat in a model Tank.
So my answer is. You're completely OK leaving them as they are. Just enjoy the engineering perfection of having "ball race" or "needle race" bearings in your Tank.
All the best,
Nick.