I rarely use sugarpaste (fondant) with CMC to make cake toppers. I find it difficult to get a smooth finish.
I use either:
These are the amounts of CMC I use:
- plain flower paste (gum paste) without CMC
- or the 50/50 FP/SP mix with CMC.
- A 50/50 FP/SP mix is a mix of flower paste (gum paste) and sugarpaste (fondant) mixed in ratio 1:1. F.ex. 25 g of FP and 25 g of SP. You don't need to weigh the paste - just mix similar size pieces.
- About 1/2 teaspoon of CMC per 100 g of 50/50 FP/SP mix if I want the paste to be quite thick (f.ex. a body that doesn't need a lot of shaping).
- About 1/3 teaspoon of CMC per 100 g of 50/50 FP/SP mix if I want the paste to be a little softer, but still hold the shape well (f.ex. a body that needs more shaping but still needs to support a heavy head).
- About 1/4 teaspoon of CMC per 100 g of 50/50 FP/SP mix to make parts that don't need to support any weight (f.ex. arms or tail).
If you are using different types or brands of paste you might need to use less or more CMC. So if I were using sugarpaste (fondant) instead of the 50/50 FP/SP mix, I would use more CMC (sugarpaste is softer than the mix).
Since I add the CMC shortly before forming a certain part, I don't just take 100 g of paste and add 1/2 teaspoon of CMC to it. Instead of that I take the small amount that I need f.ex. 30 g and add the amount of CMC that I think is enough (I don't measure it). I knead the paste. If it still feels too soft, I add a bit more CMC.
The more cake toppers you make, the easier it will be for you to asses how much you need to add :)