A pair of sure-grip inserts formed as molded rubber sheathes for use in conjunction with a caulking gun having a downwardly protruding trigger that is retracted by hand to dispense caulk, and a downwardly protruding stationary handle to provide a hand grip for retracting the trigger. The trigger insert formed as an open-ended molded rubber sheath with a particular contoured shape and an internal channel conforming to the trigger for slidable insertion thereon. The handle insert is likewise formed as an open-ended molded rubber sheath conforming to the handle for slidable insertion thereon. The inserts are molded per a two-color double-injection-molding process to provide an aesthetically striking two-color appearance, and they are molded with a particular contoured design that conforms to the hand, thereby improving comfort during hard, extended use. The contour plus the use of soft-durometer thermoplastic rubber gives a high-coefficient of friction for a vastly improved grip under all (even wet) conditions.