yep you have to do it by hand, filters will only do so much, I dont use them except in certain circumstances.  If I am painting over a photo I make a new layer and paint what I want on it, using it as a guide, or adding to it and blending it together.  I use the same method for renders, and there is a ton of stuff in my gallery in this style, and other styles, and some are just renders or photos...I work in many different mediums.