2nd: ice the cake and use a fork and run the tips of prongs into icing to make squiggle/straight lines (squiggle is more forgiving)
3rd: ice cake and use tip of spoon and dig little trenches going around the edge and random on top
4th: ice cake and use a butter knife tip and drag it from bottom to top around edge and from edge into the center on top
Now you never have to worry about making the icing all nice and smooth (which will give you a quick headache). Use these designs with butter cream or any soft icings like cool whip icing. I hope you enjoy!