File only, would be hard to justify a good grinder in my case. If I'm running out of daylight in the woods, I will just quickly throw another spare sharp chain on, otherwise I find a stump I can get comfortable at. Back in the shop I stick the bar in vise and trun on some tunes. I found that Stihl chain is harder to sharpen and dulls the files faster than Oregon. Not sure if it lasts longer in wood though, guess it does if its harder.
Dave