How to put blush on face in Photoshop?

I wonder if you are over complicating it in your mind.  Keep it reasonably simple, but we can certainly give you some tips.

Make a new layer

Create an elliptical selection — the size and shape is not critical at this stage.

Fill the selection with a colour close to what you are looking for.

Make the layer a Smart Object.  This stage is a no brainer for several reasons.

Note:  I have already blurred the layer, so I have used Free Transform to show the unblurred original.

Use Gaussian Blur to soften the red(ish) disk. Because the layer is a Smart Object you can double click 'Gaussian Blur' at any time to reopen the dialog box and adjust the setting.  I have also reduced the layer opacity to 50% — it's feint because the other dialog box is open in this screen shot)

My prerred means of adding skin texture is Camera RAW > Effects > Grain

I used a value of 15 in the above screen shot, but increased it to 25 for the 100% zoom screen shot below.

The grain needs to be barely visible, but like the Gaussian Blur, you can fine tune as many times as you need because the layer is Smart Object.   She looks like a circus clown here, but you would adjust opacity to suite.

Fine tune the colour by clipping a Hue/Sat layer to each blush layer.

Clipping means it only affects the layer it is clipped to, and you do this by clicking on the icon I have highlighted at the bottom of the Properties panel.  I have obviously gone crazy with the hue adjustment, but you can make it any colour you want by adjusting those sliders

Use Free Transform to adjust size and shape.

Do you need help with matching the colour to an existing colour in another image?

Please post the image in question.