Shooting long exposure photos in daylight can create beautiful images that capture movement in a scene, but the filters required can be prohibitively expensive for casual photographers. As this video shows, though, all you really need is a cheap piece of welder's glass. Usually when you want to shoot a long exposure photo in daylight, you'd need to use an ND (neutral density) filter to dramatically cut down the amount of light that enters the lens. That enables you to expose your film or camera sensor for longer periods of time (say 30 seconds) to create that glossy motion blur effect. Professional ND filters can be expensive, but as photographer Mathieu Stern points out, all you really need is a piece of welder's glass that you can buy at the hardware store for a few dollars. As the name suggests, these pieces of glass are normally used in welding helmets.
Mounting the panel of glass might be a little tricky, though. Mathieu just uses rubber bands to secure it in front of the lens, but even if it falls and breaks, it's just a few bucks.