While editing this picture, which was shot in JPEG, at one point some noise got added to the sky after I increased the saturation. I knew that the luminance noise reduction in ACR would take care of this. However to do so, I had to save the file as a JPEG and then open it again through ACR, apply noise reduction and then replace the monument with it's layer in the older .psd file (since I didn't want to loose it's detail).
So, I was wondering if there was a way to open a layer directly in Camera Raw and then process it then and there to avoid all this hassle?