As this is my first entry, I only have 3 steps saved (didn't think about it).
My first step was to create a new layer and select "Mixer Brush Tool". And be sure that "Sample All Layers" was selected (as this makes it possible to blend/paint the colors from the source img to the new layer). And started to roughly smooth out the rose.
step 2 of 2
Here I've started on the leafs etc. + added some more detail with a smaller brush size.
But this is pretty much it. Only used Mixer brush tool and eraser tool. Why end ressult is a bit different from this one ;p