DDH-09 mod with gaianotes putty [HELP!]

Hi everyone! I'm very very new to dolls and this is my very first faceup(?)/mod. I received a DDH-09 (flesh color) with a faceup and modification to the mouth so it's smiling with teeth. I've removed the faceup it came with since I want to paint my own, and I also wanted to cover up the open-mouth smile that it had. I also wanted to mod the eyes.

I used Gaianotes instant color putty in Fresh to close the eye holes up a bit. This pic is after a rough sanding but I'm happy with the shape thus far! Will continue to sand further with e-file and smaller grits.

The one thing I'm worried about though is the mouth - I want to have the mouth area flat so I can keep things simple for myself and paint on a simple smile... but I know that top lip contour is from when the head originally had lips. I'm wondering what would be the best way to achieve a flat shape around the mouth area? Or should I attempt to sculpt a pair of lips? I'm unsure what to do since my coverup with the putty looks really off 😕

I'd also like tips on how I can blend the colors (of the putty and skin) together. I'm thinking about mixing a shade similar to the skin tone and airbrushing it on top before I go in on the faceup. Gaianotes putty is a close match but it's not quite the same color.

I realize I've probably picked a very difficult method for my first time working with dolls ^^;; so any help would be really appreciated!

Could you sand down the top lip area slightly? 

In regards to colour matching, I don't own an airbrush so I wouldn't be able to advise there, but pastel is often a good way to match colours. You can either blush the dry pastel on or mix it with water, paint a layer on, and blend when dry. It can take several layers to build up a consistent colour with pastel, and the colour can be uneven at first, but blending it/buffing with magic eraser helps that between layers. 

Are you going to give them any eye makeup? Blushing around the eyes could help hide some of the colour discrepancy! If you have a look at some doll artists on insta/twitter, many of them use a peachy colour to add depth to the eyelid, or a soft brown around the eyes. 

From what I've seen from other faceup artists who use putty, by the time you add blushing with pastels and paint it's pretty hard to see the line where the putty ends, especially around the eyes. Airbrushing could also work! It's also possible to work design elements into the area to help if you still have some problem areas, like eyeliner, a mole, or makeup.