I don't think you got the answer you wanted. It is very technical so here goes:
I think by brightness you mean an image with more shadow detail and with overexposure of brighter elements like the afternoon sky, snow, etc
The increased brightness on a DSLR is caused by an amplification of the light received into the DSLR and converted into an electronic signal.
For the sake of simplicity your DSLR's true iso is actually the lowest one in the camera, although some exceptions exist. When you choose a "higher" iso you are actually increasing the electronic signal received per pixel on the sensor. So if you meter a setting where appropriate iso is 100 and you increase it to 400 you are increasing the signal per pixel by 2 stops.
Film does not work like a digital sensor. This means that the film speed rated by the manufacturer is the minimum appropriate speed for the film. The ISO rated is part of exposure value, which also uses shutter speed and aperture for calculation. This means that 99.9...% of the time you can rely on this film to produce the correct exposure for an exposure value of everything in your frame.
This also means that to get the overexposed look, you can simply expose the film as if it were a "slower" film. This means shooting iso 400 film at 200, 100 or even 50 iso. However, the final image will not always be like what you see on a dslr, as you may be able to retain more highlight information than on a DSLR when you scan the image.
Bonus fact: as a rule of thumb modern digital cameras are better at recovering shadows than highlights, while film is better at recovering highlights than shadows. This is because of the way that DSLRs work to get you the "overexposed" look. For film, light is your friend and overexposure might even be better in many cases. Consider a tripod for nighttime shoots and nothing will stand in your way - except maybe reciprocity failure