I've never grown dewberries, so have no direct advise. Similar to blackberries, so try that search as well.
All hormones (plant and animal) are effective at extremely low concentrations. Follow the label as to use, using too much can be harmful as well, so don't think think that if a little is good, a lot will be better.
Transplants will be your fastest way to harvest. Prune the cane back to an inch or two when transplanting. This will stimulate new sprouts while giving the roots time to recover/grow.
Easy way to produce quick transplants is to pile soil over trailing stems and keep them watered. When the stems root, cut from the main plant, dig up and transplant.