Using overlay on multiple drawings per cel


So I watched the youtube videos on shading for tradigital art and i can get it right with using the overlay on a single cel with all lineart and colours on that one cel as one piece, but because i have broken my characters up piece by piece so it is easier to reuse animation from the library ( heads, eyes, torso etc all separate just piece together) is there any way to use the overlay on one cel just once instead of attaching it to every individual body part I have pasted into that cel? I tried flattening the pieces together on the cell but it won’t flatten. This is traditional animation, so no rigging etc. I checked youtube and i don’t see a tutorial that would work.

Normally the line art goes on the line art layer and color fills on the color layer.
You can enable the advanced animation to draw in the overlay and then disable it again after drawing your one frame. The artwork of the overlay should still show up in the render.

Why not rather do the shading using using a tone module? Just because you are working tradigitally doesn’t mean you can’t use compositing effects in the network.