Breakfree is a great product and I’ve used it to clean out carbon deposits, lubricate and for storage.

I now use Eezox instead of Breakfree, as it’s just a tad bit better at corrosion protection, but is about the same relative to carbon removal and lubricating. You'll have a hard time finding anything that provides corrosion protection as well as either Breakfree or Eezox without using a grease.

The best I’ve found for copper removal is Bore Tech Cu+2 – It’s much faster and more efficient than Sweets and will remove carbon.