I use a balsa loaded with Crox for quick touchups of razors. I also have 0.25 micron diamond on felt bench strop but never tried Crox on leather or anything else.

at the end of the day: Crox on balsa works and it was probably the best $20 I spent on wet shaving.

some people use them to finish honing but I don't do that myself, the reason: one may argue the legitimacy of this argument but I read an article by Jarrod at thesuperiorshave that stropping on pastes makes for an obtuse edge that is not the best. I myself use only 10 to 15 strokes (not laps) on Crox when my blades start pulling. and 40 laps on 0.25 micron diamond on felt.

it works very well for me but YMMV