I have a moustache, so that's easy....

The hardest part with a straight for me is just below the lower lip. I find it hard to start the stroke--whether going sideways along the line of the lip, or going straight down from the lip. I both cases starting and continuing a smooth stroke have been really tough: I don't know if it's lack of lubrication, not-the-sharpest blade (does well elsewhere).

The last few times I've switched back to DE for the toughest of it, until I get my straight skill up. I'm only about a week into it.