Yes you are absolutely right. The cream must be as oily (Vaseline is best) This cream is something like vaseline with marigold extract, but does not have to be just that. Alcohol has a mild acidity, and effectively remove fat with coins. But the sediment on a coin after the treatment is much easier to remove mechanically. The procedure is necessary to repeat several times. I mention the need to end the coin wash solution. I protect you it Turpentine oil.
Here's another example, but I ended up with a clean, Emperor Licinius