I have recently started making collage art. I have been incorporating it into my art clocks and wall organizers. I find it very enjoyable. I have been transferring images by spreading gel medium on the image and pasting it to my surface and rolling it with a barer roller to get bubbles out. Let it dry for a couple hours and spray with warm water and loosen the back of the paper with your finger and remove the back of the paper. Image Transferred.
Tip of the day is you can use any type of gel medium as long as there is polymer in it. Spread it with your finger it works better.
Also with this technique if you make a mistake and don't like something you have done just go over it with paint and another paper collage or image transfer..