For bindings with purfling, I just glue the purfling to the bindings, spritz with water or whatever, wrap in aluminum foil, and bend them over a form with a heat gun. Tape it down over night and good to go in the morning. For forms I just use quarter inch plywood cut out to the profile of the body and put it in a vise. Not really that involved... I've never bent a herrignbone rosette although I have some and have thought about the idea. Here is what I would do: I would take a piece of scrap plywood, route out the size channel I wanted, then lay the herringbone strip at the top and with a water mister and heat from a heat gun (not too hot) work that herringbone strip in there slowly, hit it with a big blast of heat at the end, let it sit overnight (or not) to dry and then take it out and good to go.