
After some research and evaluation of third party solutions I settled on Zazzle for this purpose as they offer a production and distribution channel which means I can get on with what I am best at. Ideal.
I create the designs and they do the rest.

My Zazzle store is configured to update my websites automatically. Zazzle updates Facebook which in turn has been setup to send posts to Twitter. Twitter content is then fed back to my website. So, updating my social media is a breeze.
Once you have a setup like this it pretty much runs itself. You just create your products, upload them and decide what to write, once.
There's a few little extras you'll need to do like attract Twitter followers and Page likes, but the real drain on resources is cut to a minimum.