print the fish image on tissue paper and glue it to foil (or foil tape) and then glue (or stick) the foil(tape) onto your bait.
you can print on tissue paper by taping a piece of tissue paper onto a piece of printer paper (dull side of the tissue up). be sure to completely tape the edges down, or it could foul up as it runs through the printer. only tape the edges though.
i have found that if you do the tissue/foil method, you get a decent image that is reflective, however, if you just print on printer paper and then glue that to foil and then on the bait, it provides more detail but its not reflective at all.
the easiest method i could think of would be to just use full sized adhesive sticker paper in your printer. you can buy it at staples, etc. i really want to try this. i think next time i go out i'll pick up some of this adhesive paper and try it out.
heres a great tutorial on how to photofinish: http://www.tackleunderground.com/forum/hardbait-how/12431-photo-finishing-foil-faux-finishes.html