Below you will find some some things that worked good and some well lets just say....not so much!
This is my first attempt at doing fondant on a sheet cake. Mistake #1 ~ I could not find my smoothing tool that was sitting on my counter right under my nose!.. I was not supper impressed as the fondant was a little dry and cracked in places. The lesson I learned here is more moisture content in the fondant on larger cakes for a smoother appearance!
I thought it would be pretty to add some blue roses (I used tip # 102). However, because of the soft nature of my butter-cream which I had pretty thin to do the dots and cross. My roses did not set up (again should have used a thick butter-cream or royal icing for them)- but they were cute so I'm posting a picture of them even though I didn't end up putting them on the cake .
New technique #3 ~ Painting on a cake with diluted gel food coloring. (small amount of water on a brush dipped into lid of color worked great for me- doesn't take much water to get a paint consistency) Again, few errors made but liked how it easily wiped from the fondant with a damp paper towel. I also practiced on my "scrap" fondant to get the consistency I needed for painting.
Overall, I am content with this cake; it had a lot of firsts for me which is why I was "experimenting" on a cake for my family as opposed to one someone ordered. :)