There was a lot of trial and error and many throwaways. I didn't have a concrete source of information to work from and opted to take what I could from various online and book sources. The interesting thing about these transfers is that there are many, many variables and some methods work better for others.
I'm my case, I kept much of my supplies constant and experimented with matte medium consistency. I also had issues with color transparencies but I believe that was due to the printer, not the transfer. I had run out of ink on my semi-pro Epson 1900 and choose to use my home printer which is a Canon 3-1. I believe that the way the printer lays down the ink explains the loss of magenta in the color transfer seen below:
What worked for me was to let the transfers sit on the gel medium for at least an hour. I found that more detail was more intact and transferred better when I peeled off the transparency paper.
These are the materials that I used:
-Arches 140lb Hot Press Watercolor Paper
-Golden Gloss Gel Matte Medium
-3M Ink Jet Transparency Paper
-Small Paint Brush
1. Prepare your image. Print onto the transparency paper. Make sure that you are flipping the image before printing! I profile my images for glossy paper and the image quality is satisfactory. The nice thing about 3M paper is that there are two very distinctive sides to the paper, a rough side and a smooth side. You will need to print on the rougher side of the transparency.
2. Prepare your paper. I buy very large 20x30 sheets of watercolor paper and for these transfers, I printed small, 5x7 images. I used a bone folder and tore the paper down to an appropriate size. While my images were printing, I dampened the watercolor paper with water and blotted it dry with a paper towel.
Next, I applied the gel medium. In this step, I experimented a lot with the gel medium consistency with water. Too watery, the image will bleed and the ink will run. Too dry, the image will not transfer. As much as the consistency of gel works with tranfers, I ended up mixing a bit of water to bring down the thickness.
3. Apply your transfer to the paper. With the gel medium/water mixture applied to the watercolor paper, take your printed transparency and place the image onto the readied surface. Gently apply soft pressure to the transparency and smooth out any air that might get trapped underneath.
4. Now this is where I veer off from any other conventional set of instructions. Many other instructions tell you to apply pressure and rub the heck out of the transparency print onto the paper. I end up letting the transparency sit on the paper for an hour. After that, then I begin to apply pressure to the transparency, using my brayer to push the transparency print on to the paper.
5. Carefully lift off the transparency. Allow the paper to dry. Done!
Good luck and remember, this is just ONE method that worked for me. I'm still not that satisfied with the end results and I would still like to achieve a full colored print. Either way, if you are trying inkjet transfers and have any questions or comments, feel free to let me know!