Observe that the 'sky' was applied first, then the 'horizon' then the barn, the ground, the tree, etc. Scenery in the front should be ON TOP of the sky, ground, etc. Use brushes that work well for you. I like to use a fairly large-pointed type. The brush should be big enough to pick up globs of icing.
Flowers are merely dabs of icing in a raised affect.
Raised affects add 'life' to your cake pictures. The icing is fairly soft and the brush needs to be medium pointed brush for most things - Different strokes, different effects different brushes. An oil painting instructional book is helpful for coloring tips. Dissolve soda in the soup. Cream butter, beat in sugar and egg, add soup mix and beat well.