I would say apply buttercream on the styrofoam direct as you would normally do to a cake. ( have never done it though) if i had to, thats what i would do. another idea may be to apply a very thin layer of piping jel, and then apply the bc. would love to see what other ideas would follow.
Not sure if my answer to you is silly too. if its a small pot why not make it with 50/50 fondant/gumpaste. shape it into a honey pot. colour some piping jell and place over the pot. if its a big pot make it with rkt. i would imagine like a ball shape. once you have covered it with bc or ganache, cover with fondant and make a little neck and collar for the top of the pot.
To my knowledge, you use 50/50 to mold whatever you want to make.if you use only gumpaste its expensive and it dries very fast. using 50/50 it gives you time to adjust after making the item. only fondant is a bit too soft and takes longer to dry.
Not sure what the zig zag ribbon on the mold is. apply some veg. shortening lightly inside the mold and place the fondant/gumpaste in the mold , press, and cut off excess. place in the freezer for 20 minutes and when you open the mold gently take the pearls off. there is a tutorial on the internet
I think you should take it out of the fridge. the buldging may be due to excess icing underneath the fondant. What sort of icing did you cover the cake with. most probably it hadnt crusted. I dont think you place fondant covered cakes in the fridge because they start to sweat, i am told. i hope someone will come up with some advice.
i made one lately. got tips from this site. i boiled some sugar and when it was a bit caramelised, i placed the skewer on a piece of baking paper and then poured the sugar over it. while it was still warm i rolled the paper just to get all the sugar around the skwer. i placed the skewer into the cake and placed the can at the top. I had to send quite a bit of the skewer into the cake as the weight of the can kept moving the skewer. eeezzzzz.