Last year when I started shaving with straights and honing my own razors I lapped stones with wet/dry sandpaper on glass. It certainly worked. I found though, that for me it was really a one use per session thing as the paper backing after it would dry out would exhibit the same behavior as any paper, it wouldn't dry flat (a huge no no for reusing then to lap a flat surface).
Do others find the same?
I never tried to keep the wet dry paper wet and assume it would either end up degrading or would also result in a less than flat surface. I found wet/dry to be spendy and even cutting it in half to save paper, I found that it wouldn't be cost effective over the long term for lapping. It really wouldn't take too many packs of wet dry to start getting up to the cost of a DMT D8C that would last for years.