You do not want to try to adjust focus while filming with the glidecam. Before you shoot, put your shutter speed to 2.5 times your frame rate. Jack your aperture up. Adjust your iso to a non grainy level where you can use your aperture to adjust exposure. I usually keep it in between 9 and 16.
This way everything is in focus and you won't have to worry about focusing. This doesn't work if you are shooting anything close up.