I have this very intricate cutout with very bright colors. They are so bright I like them better when they are in multiply blend mode against its backdrop. However, I can't leave them that way, because I need to export these cutouts to use them as transparent pngs in an interactive way later. So what's the easiest way to get these cutouts in the shade as if they are in the multiply mode? I mean potentially I can re-edit each individual cutout by changing its curve and saturation, but what would be a good workflow for this? Any suggestions?
Without seeing your artwork, it's hard to tell if this will work for you, but here's my suggestion:
You have a layer with a cutout:
You think the colors look better when multiplied on the background below:
Ctrl + click the thumbnail of the cutout layer to create a selection using that layer's opacity:
Select the cutout and background layers, click the Create a new group button and finally click the Add layer mask button.
Now you have the same opacity as before, but the colors of the cutout are blended with the colors of the background layer.