I find the US International keyboard layout to be useful to me.
On a Dolch keyset, I put Scotch tape on the front of the keycaps and mark the legends with a white gel pen used with dark paper, specifically Gelly Roll 08 from Sakura. The "ink" dries like a kind of paint. These seem to hold up pretty well as the front of cap doesn't get a lot of wear. However note, gel pens in other colors don't mark the tape anywhere near as well.
On a Biege keyset, I do same and mark the tape with a 2B pencil, then place a second piece of tape over the pencil to protect it.