I just finished my first attempt (for this project) at a toner transfer. I always inspect my boards with my flatbed scanner. I highlighted the unacceptable problems in red.

As you can see, the errors are small, but in critical spots. This board is a little too small for a sharpie touch-up, larger boards are way more forgiving. Next step, clean the board and try again.

Once i complete this step satisfactorily, i'll reveal my secret sauce in the instructions.