I used filters on top of each other.
First i used cutout filter to reduce the details.
Then some artistic filters like brush strokes.
Along with this i also apply gradient overlay adjustment layer on a copy of previous work.
I think, even i tell you whole process, still it needs some manual adjustments and layer masks.
it's good that you try it yourself. share it with me on ( steemit.chat ) and i guide you for next step.
... May this help you friend ...
... great day ...