Touchless gesture interfaces enable user interaction without the need for direct physical contact. Recently there has been increased interest in deploying such interfaces over concerns about touchscreen sterility. Many touchless displays use gestures that mimic pointer-based interactions, with a cursor mapped to finger position, that users activate by pushing their finger forwards. Mid-air pushing with a virtual cursor is fine for discrete interactions like button activation; however, users have difficulty exerting control over continuous interactions like sliding and scrolling, because it is challenging to keep the hand at a consistent depth when gesturing. We investigate interaction techniques for slider control that use alternative mode switches between (un)pressed states. Our findings show that pinch gestures are preferred by most users and offer a faster alternative for acquiring control of sliders, as pinching has two clearly defined states and avoids the ambiguous use of depth for delineating input states.