We've been doing this with plain hair gel and food such as tinned spaghetti, custard etc for years. I decided to make a Christmas version by adding glitter and Christmas confetti to the gel before putting it in the bag. Its a great activity for children who don't like the feeling of gooey messy stuff on their hands as it is a 'safe' way to explore the textures. We've progressed on from being quite so defensive but James did play with this 'bagged' for much longer than he would have done if he had actually had to touch it and anyway, it's fun!!
I usually use the sealable bags to do this and put the filled bag inside another one to minimise leakages. This definitely needed 2 bags as the stars started to poke through the plastic. You could tape the top but to honest, I never have.