How would I create a sponge painted effect on a cake. She told me her last decorator(before she moved) looked like she used a paper towel or wax paper to put the color on the cake....

Any ideas, I can't even picture what this would look like?

Here is a link to sponge painting on fondant covered cakes. HTH

http://www.wilton.com/technique/Sponge-Painting-Fondant

Do you think that technique could work on a crusted buttercream cake?

a crumpled up plastic grocery bag will do the trick too (my mom did that technique on a wall a few years ago and refused to pay $10 at home depot for the sponge required LOL) so she improvised..looked exactlly the same and didn't cost her a dime! I would imagine if you're worried about food safety that a piece of crumpled plastic wrap or waxed paper should do the same trick!

I buy a brand new sponge, cut it into small pieces, then wet it a bit, wring out well. Now, dip it into the diluted food coloring, and voila! Works beautifully. I've used this effect many times on the sides of my book cakes to look like the pages are colored like in religious tomes. For those I'm using 3 colors, but for a general sponge effect, just use one color over white fondant, for example. Hope this is what you had in mind, (you can first practice on a small piece of fondant.)

i think a sea sponge would look nice, you can get them at home depot cheaper than craft stores, i bough this something in the kitchen dept in the dollar store has a black handle and has a swirly thing on the end, let you know what it does lol