Think you can do all the steps in that face retouching tutorial in AP, but I wouldn't. I think there are now better ways to do those steps, for example for noise use Noise Reduction, to blur the flat areas of the face use Bilateral Blur. In Dan Margulis's book 'Photoshop LAB color' he gives a simple way of enhancing faces that I think gives a better result than that tutorial.
To get rid of the yellow tint when you blur the B channel, blend the original layer with the layer with the blurred B in colour mode (you'll see the yellow tint) then use the controls in the bottom third of the layer options window: tap Master, select Red and Green in turn and for each, in the box on the bottom left, drag the horizontal line from the top of the box to the bottom. This selects the R and G from the original. Apparently blurring the B changes the R and G slightly; I'm not sure why.
Hi, my bottom layer was the original. To create the second layer I duplicated it, went to the channels studio and tapped composite blue to just display the B, then tapped the filter studio and applied a Gaussian blur - this is applied to the visible channel only of the second layer, B. Then in channels studio I tapped the return arrow at the top to display all channels again. I then changed the layer 2 blend mode to colour and saw the yellow tint. Which I got rid of with Blend ranges as I described above.
You seem to be turning an RGB image into a single channel by adjusting the curves to zero the unwanted channels. This doesn't seem a useful thing to do.
