Hope this might help someone.. I blindly acquired a Yamaha Trb5ii fretless from evil Bay and only realised on delivery that the side dots are in the wrong place! ( like on a fretted bass but this is a factory fretless) Although the fingerboard is faintly lined it is difficult to see from a playing angle and I always go by the side dots anyway. I tried to adjust to having them in the wrong place but found it infuriating! So, I masked off the areas that needed marking with tape and put on some white acrylic paint that can easily be scraped off with a finger nail if done badly or for removal at a later date. Now a great bass is really playable. This took no more than half an hour. Here's a link to a pic as I can't figure out how to place a photo here.
https://www.dropbox.com/s/xe8ssjbi2c03dvq/IMAG0216.jpg?dl=0