Hi,
A teaspoon of sugar (brown) is said to help but i have never needed it, I learnt this method working in hotels.
I''ve always found it work. Make sure the coffee is still, put a teaspoon as flat as possible, bowl down, into the coffee so the rim of the spoon is the same level as the coffee, with a little coffee is in the bottom of the bowl, and slowly fill the bowl with cream and let the cream rise and float over the top of the bowl and on to the coffee.