Experiment and see for yourself;not all symbols work the same for all people,they are rather general.
You can go by using online or paperback dream dictionary then compare and create your own image/meaning journal, while drawing conclusions from your own experience and practice.
Experiment with different brands of coffee and cream like double,single and so on.
The most reliable source ,when dealing with divination of this type, is yourself and your own subconscious finding patterns and images in certain type of material or liquid.Because you have to start from somewhere and build confidence , start with randomly picked brand,or you can use pendulum to validate which is the best for the scope.
Use the dream dictionary or archetypal ideas,and see if the divination makes a sense in this way ,keep a track on that in your journal and see if particular images appear more often before event/s.If you have had already dream journal,such can provide some extra information for your divination.