Before this handy tool was invented .... here's how most of us model ship builders bent our planks.
First we soaked them in warm water in a old coffee can or mama's silver water pitcher (when she was out shopping). Then we took a knife and scored one side of the plank every few fractions of an inch. Of course, you know what that did ... it allowed the plank to bend easily on the scores. Try it .. it works.
Mantua Model picked up on this technique and devised a plier-like tool that does the same thing but better and faster. Check out the photos. The tool has all kinds of added widgets to help you get the exact bend you need to properly finish that bow.