I think your thinning ratio is a bit high.
1:10 is too high. 1:4 or 1:5 is more than enough. What important is is to have thinly applied glazes, not overthinned ones.
On a figure that big, bigger brushes can help with a wet on wet technique, but that is pretty advanced and requires a fair amount of retarder to keep the paint workable on the surface.
I agree that a big brush helps as is wet-in-wet. But it's not an advanced tech. In jarhead's workshop people used it who have painted 1 or 2 minis so far with excellent results. What's hard is finding someone to show it once.
So far the only 'online' resource I know of for it is JBT's second DVD (paintingbuddha's Ben uses a wet-in-wet that's quite different).
(for the lioness bust I have in my gallery I used Jarhead's fast version, the whole bust was painted in 2 or 3 hours with the wet-in-wet part being about 5-10 minutes at most.)
Another approach would be to use pigments which can be blended wet or dry and sealed once you are happy, again more advanced than you make like right now.
yep a wonderful way of working with pigments. so easy. I shaded/highlighted the astronaut's helmet in my wip with pigments only. No glazes or any water

(similar with the skin of the naked anime figure (the first where I used dry pigments for shading))
And again I disagree with the difficulty. it's super easy tech not really advanced imho.
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I also want to give her auburn hair so I'm worried that I've made the wrong choice going with a yellow toned skin colour. Maybe I should have gone with a bluer undertone.
don't worry about that. you can always adjust the tones with glazes. And right now you are still missing a LOT of contrast. By using some cooler colors(even unlikely ones as spacewolfgrey (light grey with blueish tint) in the highlights you can change it.
As for the pic: I wouldn't strip the paint. you made yourself a lot of work with the dilution, but so far it looks good. what you need is more contrast like:
- extra shades with blue or purple mixed in the color
- extra highlights above the mouth, cheekbones, forehead, busts with ivory or even pale blue mixed in.
I don't think this blogentry will help as it's not in english, but:
http://ma5xfestesek.blogspot.ie/2014/07/noi-arc-festese.html (at least the palette used for the face and some steps are visible)