An apparatus can aid usage of a plunger, for example helping a medical practitioner use a hypodermic syringe to inject dermal filler. The apparatus can fasten a thumb rest of a plunger of the syringe to a thumb of the practitioner and can support one-handed operation of the syringe. With the plunger so fastened, reverse thumb motion can retract the plunger for aspiration, and forward thumb motion can advance the plunger for injection. The apparatus can comprise a member extending at least partially around the practitioner's thumb. The member can comprise an aperture configured to retain the thumb rest between the thumb and the member, with a shaft of the plunger passing through the aperture.
