Ah, there's nothing like a bit of kitchen chemistry... :)
I used this technique to make a couple of single sided Arduinos
I also tried the vinyl film method
just now, using an offcut of Kittrich Clear Liner which is inexpensive glossy transparent adhesive PVC sheet (less than $5 a roll). I stuck a rectangle of the liner on a sheet of paper and printed the resist mask image on it. I transferred the image to the copper clad board by pressing lightly with iron on the maximum setting (160 oC) over a rolling pin for 1 minute, then carefully peeling off the plastic film while the board was still hot. I was worried that the 16 mil traces looked "hollow" and went overboard with a Sharpie. I think I worried unnecessarily although it was not a big deal -- the traces were easy to touch up without paper fluff everywhere. The board etched satisfactorily with no defects and far sharper detail than I have ever achieved with paper transfer. For example, the board was noticeably easier to drill because the tiny drill-aid.ulp lines were properly etched, making it easier to centre the bit.
This is definitely a method I will try again. The disadvantage of hollowing of black areas is outweighed by the fidelity of the transfer in other respects and the ease of touching up. It also requires less heat, pressure, and time than paper transfer.