Can I use a crusting BC as accents on fondant? I'm doing a mermaid cake for a friend's daughter (first cake I'm actually sending out the door; yikes!!) and using the Wonder Mold pan for the mermaid part, but want to set that on a bigger round covered in fondant. I need to know if I can make the seaweed, flowers, etc. out of BC, or do I need to use RI? I just don't know if they will slip off. TIA!

You can use all that stuff on fondant--no worries.

As you know my post was very similar to yours (since you were helping me out )
A few of the replies on there was that RI is best for decorating on fondant. That's what I would use on my barbie cake if my daughter weren't allergic to egg whites. When I googled this same topic a lot of the responses were to use RI.
I am definitely a newbie too, so only going by what others told me.
Good luck and post a picture when your finished.

It'll be fine using buttercream instead of royal icing. I have used buttercream on fondant and have had no problems.