Below is a brief explanation of how I use Citra Solv Concentrate to transfer toner based prints to faux leather. I also use it around my studio and home as a high quality cleaner/degreaser. including cleaning metal, brushes and lithography/intaglio inks etc.
Contact Citra Solv directly to get discount coupons and to purchase it near you. I find it in my local natural foods store and for convenience I put it in a small pump spray bottle and I do not dilute it for most applications. It's best to spritz this carefully, though it is a non-toxic cleaner it still is a powerful solvent.

Moderation, common sense and careful handling are all recommended.  Any liability loss or damage associated with any use of the information contained in all FAQ is expressly disclaimed.

Above top is Corpus Neo A Concertina, water color paper, leather cover with gold leaf and gelatin monoprints. 8.25" x 6" 4 pgs.
Above bottom left & right pages from Golden Ratio Relief monoprints, with Citra Solv toner transfers, 6.5" x 4" 12 pgs.

I use Citra Solv Concentrate (full strength) as a transfer medium to transfer photocopier/laser prints from my Brother MFC 7440 (multifuntion printer fax copier that uses black only toner) to various different surfaces. For the artist's book pictured here I used Citra Solv to transfer the Corpus Neo lettering onto the faux leather cover. When I was done transferring the black toner onto the pleather cover it was nearly invisible, (black on black) BUT what is transfered is enough of the toner surface that gold leaf sticks to it.

This is how I do it: (Just one of the many ways I use Citra Solv Concentrate)

In Photoshop I layout my text. then I reversed the text and print with my Brother MFC 7440 onto a sheet of plain paper. (Text can be printed from Microsoft Word and flipped horizontally when you send the print to the printer.)
After the text is printed I put the print face down onto the book cover.
Next I spritz a little Citra Solv Concentrate directly on to a paper towel LIGHTLY saturating the paper towel with the Citra Solv Concentrate, then I place the paper towel on the backside of the face down print.
I gently rubbed the paper towel to carefully transfer the Citra Solv Concentrate to the backside of my printed paper. *The goal is to moisten the back side of the print with Citra Solv Concentrate but not make it too wet. It is necessary to do this gently as the toner (the printed letters) will smudge if you work it too much or it is too wet.
You will notice the printed paper becoming translucent once the it is lightly moisten with the Citra Solv Concentrate. Once the print is translucent you can remove the paper towel and gently rub the back side of the print.
Continue to rub the back side of the printed paper gently to transfer the toner. I use a bone folder or the back side of a spoon. Carefully hold your paper in place and look at your transferring text by peeling back your print.

On the faux leather the transferred text was barely visible but I could see it. I laid a piece of gold leaf on top of the transferred toner and gently rubbed the leaf into the toner. It holds! I do wait for the Citra Solv to evaporate and then gently brush away the excess gold leaf. Not perfect but suitable to the whole look and feel of my artist's book.

If you want to learn this technique its best to practice it a few times transferring photocopies or toner to paper or cloth. The Citra Solv Concentrate will dissolve some plastics, and why it didn't melt this faux leather I do not know. The gold leaf has lasted for years and I also have no idea why it is holding to the transferred lettering and not the faux leather. I just know it worked for me and I love the results.

Below left, Spritz bottle, Citra Solv bottle, bone folder, paper towel, toner/photocopy prints, red gelatin monoprints.
Below right, Sample red gelatin monoprint with lightly saturatued toner print, lifting carefully to check the transfer progress.