Thank you all for the advice!
I don't have these shiny metallic sheets but we have a thick duck feathers quilt. Our bedroom is now at 5°C 

I lent all my extra quilts to students, I feel so bad for them! It's a boarding school so they stay 2 weeks on the campus then go home for 2 days. They are all out of power too and started to organise speeling with friends ^^

For your shade of orange I'd go with paint too, you could also ask some other member to airbrush it for you if you wanted (thinking about colorscrapeart painted baits here).
Red, orange and brown dyes leak A LOT and for a long time! Eye painting will be tough as the dye will leak through white paint and even symbol might be tricky.
Also, as some others said, G4 have a different plastic for head and body which will make color matching tricky.

Not too fond of the eye but that might be because it needs some more details?
I love the symbols you did though! Pair pens give a nice smooth result
I remember using some to get smooth regular lines an it worked just as we'll as for you. Don't forget to seal your work though as this paint is VERY sensitive to scratches!

Hi Emuel!
I have not so good news for my package. I just got a call from Hong Kong customs, they check all outgoing mail for threats, outgoing antique items and such and seems like my tube of chocolate condensed milk looked suspicious so they tore my box open. They proposed to toss it all in a bag and send it back to me I hope nothing will get lost!
As soon as it reaches me back I'll add the extras I found meanwhile minus any liquids and send it back to you. So sorry about that it's already the second time local post makes me angry! Previous time it took 3 month for an item to arrive and I got a neg on eBay
Now I need a proxy to see your brags so far!

I love the idea of hot glue masking but maybe it could be tricky to get off the hair? How about using some Modge podge instead? If you apply dye with q-tips and mask the areas you want to remain white with mod podge you could wash it off rather easily afterwards?
I'd love to hear about your trials!

That's a nice sum up of all the info we need!
For the record, I made my website (customall.net) to sell different types of pony hair but it turned out way too time consuming and only got few orders as I only propose "special" hair. So now, I keep it up for information and I'm working on distributing the hair to bigger providers as my only solution is selling through full spools (around 3 or 4 Kg each :p)

I have supplies of glow in the dark and UV changing hair, both are polypropylene (according to the provider) but I can feel a strong difference between them.

The GitD hair is VERY soft, I could keep it in my hands all day, I love the texture! I haven't used it myself yet so I don't know if it curls well or anything.
The UV hair is very delicate and very sensitive to combing. I think that's why all of our sunshine ponies' UV hair turned frizzy. Nothing to do with water or bad hair care, just too much combing! However, I think it's quite amazing to be able to have UV hair and it changes VERY quickly. As soon as I recieved my first spool, I took it out and the color changed immediately ^^

I'm still working on getting these more available, for the moment only mylittlecustoms carries it