Acetone can be found in nail polish remover, I got mine from Tesco, just look at the ingredients and see if acetone is listed, if it is, this is the stuff you want, it isnt expensive.
To make this technique work you need fresh laser or photocopier printed artwork – it doesnt work so well on older copies so make sure its fresh! The prints I used were a day old and they worked.
To make a transfer you trim round the image, place it image faced down towards the surface you want to transfer the image onto, get a cotton wool ball and soak up the acetone, and rub and dab the back of the printed image to transfer it. Lift off a corner to make sure its all transfers and then remove it to reveal your image transfer.
I transfered my image directly onto an atc which Id already added colour onto using inks and it worked fine, if your worried about messing your background up- you can always add colour afterwards.
I found this video on youtube for Acetone Transfers: http://www.youtube.com/watch?v=mv4d2zRPbG4 In the video they transfer the image onto a block for carving but I decided to transfer it onto an already inked background just to see if it would work.
I first found out about Acetone Transfers in the following book below and decided to give it a whirl, I love how this technique turned out and must do some more: