After struggling to make a Warmane Donation in order to skip the Icecrown queues, here is how I finally made one:
(Credit card didn't work so i tried the Mint way)
*Note you will need a Paypal Account (and a credit card linked to it, not sure if debit card works didn't try)
1. Go to this Mint Reseller: https://www.offgamers.com/search/index.htm?keyword=mint
2. Select a Mint prepaid card, make sure its in Euros (there are different currencies), I used the 20 euro one but that is because I'm also donating for my buddy.
3. Click buy and create account
4. After you logged in you may have to find the Mint card again and click buy again if it didn't take you to the payment page.
5. Proceed with payment, even if you select Credit card payment and not Paypal Wallet, it still redirects you to Paypal so you need an account anyway.
6. After purchasing you will be taken to a page with your order with a pending payment verification at the top.
7. Once the payment is done (you should get an email), just refresh this page and your order will be complete. Scroll down the page and you can show your Mint 16 digit code.
8. Copy this code and select Mint as your payment method instead of Visa in Warmane donation selection.
9. Paste the code and submit it.
Hopefully this guide will save others the frustration I had to deal with trying to make a donation.