Long time no see and I thought I'd post an update picture as its been over a year!
As you can clearly see, the marine grease mixed with the beeswax is a clear winner. This piece of steel has been out in direct sunlight the entire time. So my assumption is it would work better if used underneath a car.
You can see how I've smeared it onto the steel, using a single finger. Better results would be had if I had applied even coverage.
Cheers