One of the tricks to smoothing your cake it to use VIVA paper towels (they have no designs on them) Just give your buttercream about 10 minutes to crust after you frost and smooth with a spatula your cake then lay the papertowel on your cake and smooth. You can overlap on the sides for sure. I use my fondant smoother to help me smooth on top of the paper towel. If you want a pattern on your cake instead of VIVA paper towels use one with a pattern and use the same techique. HTH
Welcome to CC - there is so many good tips here!
Sarah
Most of the time now I use the VIVA towels with no patterns but sometimes the pattern adds to the cake. Yes, you can use the papertowl with pattern to smooth a cake the same as you would use VIVA plain towels or parchment. You can either try to keep an eye on the pattern or just go at it without care.
I smoothed a cloud cake I was doing with a plain towel and thought it was missing something. I then used one with an irregular pattern and it added that missing element to the cake.
Hi eema2four,
Welcome to CC...our addiction 
I love using the design patterns on my cakes. To me, it gives the cake a better looking background and my clients love it...always asking how I get the design.
You can use it on the sides with no problem.
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