How to effectively take cream from milk?
If you have raw milk and let it sit, the cream will indeed rise to the top. To separate, you can just wait and skim off the cream as you did. However, if you store the raw milk in the refrigerator, it will take longer for the cream to rise. Perhaps that is why you are having difficulties. Alternatively, you can use a spigot jar to drain the "skimmed" milk from the raw milk, leaving the cream behind.

I think you end up with about 1/10th of your raw milk that is cream.