While multi-touch devices such as smart phones and tablets offer simple intuitive user interfaces, such interfaces may not always be optimal for precision tasks typical of electronic measurement instruments. Such instruments utilize physical knobs, switches and sliders to provide precise tactile control of instrument parameters and states. This paper describes work-inprogress to investigate the use of simple transparent overlays that provide tactile guides for touch-based graphical control widgets. By augmenting the touch surface with a simple low-cost overlay, we aim to restore many of the tactile properties and benefits of standard physical controls. We have fabricated an initial proof-of-concept overlay and demonstration system and have performed a preliminary evaluation that suggests overlay guides may be beneficial.