When working with film, it's better to correct the WB before you shoot. You can buy 5600ºK film (daylight, by far the most common) or 3200ºK film. Once you have that, if you need to fine-tune WB, you'll use filters.
You could also shoot only with 5600º, and work only with filters, but since they absorb light, and you are limited to ISO400, you might want to start with the right film, and do as little WB correction as possible.
The standard filters were
80A (blue, to correct tungsten cast with DL film)
85B(orange, to correct daylight cast with tungsten film)
30M (magenta, to correct the average green tint of fluorescent lighting)
There are of course different degrees of correction (look into Mired shifts on wikipedia)
Honestly, now, I only work with film when working with the Arri 435 (most of the time, it's Epic or Alexa). For photography, digital has so many advantages, that film is pretty much dead, unless you're shooting with much larger formats.