The whipple kits are great practice and intro into decoden as the whipped cream is water soluble, so you can redo pieces for more practice.
However, if you guys are planning on using the whipple kit cream for decoden gifts/shop products, please don't!
eek I bought a few kits months ago to test out and when I checked on the whipple foods just the other day, all the cream parts had shrunk/cracked and some of the 2-sided pieces such as the macaroons fell apart due to the shrunken whipple cream.
crying However, after I used all the whipple cream, I cleaned out a whipple cream bag, let it air dry, squeezed all the air out, and then filled it with silicone caulk so that I'd have an easy way of using silicone caulk to do my decoden.
When I'm not using it, I keep the whipple icing bag cap on, and wrap the tip in saran wrap and rubber bands to keep a tight seal so it doesn't harden.
Occasionally I'll use a small metal star-shaped icing tip from the baking aisles of food/craft stores.
I just tape it on the tip of the whipple bag and use it like normal.
And when I'm done, I just wipe out as much caulk as I can from the metal icing tip and let the rest dry to later peel/scrape out.
EDIT:
DECODEN PICTURE!

This was something I tried showing you guys during one of the tinychat streams~
The bracelets finally cured and are ready for me to wear this weekend at an anime convention x3