The Baader film comes in two types, one for visual observing (eg making your own glasses) and one for photography (eg tape over the front of your lens).
Even with the film you are taking very short exposures (I can easily shoot hand held with 1,500mm focal lengths), a neutral density filter will still let through some of the harmful (non-visual) portions of the light spectrum which can damage your camera sensor if you get your exposure times wrong. So the Baader film is the right tool for the job, not an ND filter. You can add a ND or polarising filter as well if you want to shoot longer exposure times, but you don't gain anything in the image worth bothering to do that.
The images in that article have probably been processed and colourised too. With the Baader film you get a "white light" (black and white basically) image. It may be tinted blue/violet or something depending on your camera and white balance settings and may not be quite as sharp and clear as those images. You can align, stack and use wavelets though to combine multiple shots and bring out sharper detail of sunspots.
Also the Baader filter restricts the light coming through and the sun's surface will appear featureless except for the sunspots. The edge of the disc will also be smooth and featureless: no dramatic flares. The sun has a lot of spectacular features but they require special scopes filtered to reveal just those feature types. As far as I'm aware there is no other type of filter you can stick on the front of a camera lens to allow you to see strong granularity or flares etc as the light energy coming through for those can damage camera and/or lens.
A white light filter though is great. It's affordable and easy to get into solar astronomy, without long cold late nights
Hope this link works, its a shot I took during the transit of venus:
http://ocau.com/pix/4jzfm
Taken with a 500mm lens with a 2.0x teleconverter on a Nikon DLSR through a Baader white light filter. Only cropped and resized from the JPG (I processed my shots using RAWs, this was a quick one just to post an example). Camera was using auto white balance so this is how it handled for the JPG. Exposure time 1/800s @ ISO100 f/16, I had it resting on a monopod but easily hand held settings. After stacking I was able to bring out more detail on the surface than this single shot, but it gives you an idea of what you can get with your existing camera and spending a couple of bucks on Baader film.