"give away around 0.1BTC per sale of each T-Shirt"
How much are you going to charge for these shirts?
0.1BTC is around $13 or £8 at today's rate.
I realise this, 0.1BTC would be for the premium T-Shirts with artwork, sexy packaging and so on. There will also be added benefits to buying the higher grade premium shirts, I intend to create a brand that supports both affiliates and customers with prizes, ways to earn money an so on. I wont see my "customers" as people who buy the products, I will treat them as partners, I will go into all that another time.
Private Key QR code with instructions on how to scan in the QR code to blockchain.info, to then move /use the coins with other services /wallets
Yes, that or also include the 4 lines of code of the Private key itself.
Can I create the private key with Armoury? I have generated QR Codes before but I have not notices the feature allowing to add a specific amount into a the code.
Market it like those coupons where you get as rebates for your purchases. Maybe ' Get Approximately $13 back for your purchase with this Bitcoin coupon redeemable for cash!' to get them interested?
I already have the coupon system set up, I am thinking more along the lines of additional rewards which would bring new users to Bitcoin. I am also developing additional services that use Bitcoins too so I have a reason to give out these BTC beyond just marketing the product and supporting Bitcoin, I have a strategy.