Evan, the railroad chalk works pretty good. I've been using it for my aluminum files for many years. It costs about $20.00 for a gross of them on Amazon and one stick will last quite some time. Railroad chalk is very soft and builds up in the teeth of a file quickly so its easy to apply. I clean my file well, apply the chalk, then brush it off and renew it after heavy filing. I have a file that I use only for aluminum that is still quite sharp and effective and it must be 20 years old by now.
Chalk does not prevent all pinning but it greatly reduces it. I find it best for metals that tend to stick to the file teeth - aluminum, brass. I use a piece of brass to push off whatever does stick in spite of the chalk.
For steel, I don't think chalk makes as much of a difference. I use the bristle side of the file card after every 5-6 passes in steel and it works well to keep the teeth clean. I personally don't think the wire side hurts the teeth much but they don't work as well as keeping the file clean in the first place.