A brush handle is formed with a continuously arched upper surface portion and a lower surface portion separated into two arched portions by a humped semi-circular ridge. The modeling technique includes inputting tool parameters into a model and inputting basic model parameters into the model. The housing has a respective duct for each ink that extends longitudinally along the housing. Finally, as shown in the Examples, the PCR methods and devices amplify significantly more DNA compared to conventional PCR techniques and systems.