If you want to use photoshop, there are many better solutions,
Use same camera with one render with cinrender and the other with sketch render merge them with multiply layer and you will get better images
Specially the out line with celrender do not be accounted correctly..
For example. If you had one wall which you had done with 2 walls
The sketch render will give you right out line as one wall but celrender will give you the outline as two walls.. With lines between them.
I use celrender for layout , without using photoshop so when. I make any modifications it update immediately.
And maybe for this reason they keep it in one pixel