You can use any of a number of soaps and solvents. I use a spritz bottle of isopropal alcohol and a battery-powered scrubber when the stones get really dirty, but I don’t really see any evidence of the diamond stones clogging up with swarf. My diamond film, however, gets quite dirty and I do the alcohol/scrubbing thing about every other knife.
Whichever stuff you decide to use, try not to overdo it, as the plates are attached with 3M VHB (very high bond strength) double-faced tape. Some chemicals can attack the (very sticky) tape and compromise the holding power. Temperatures in the 150F to 200F range will also affect the tape strength. In fact, I use a heat plate to remove the plates from the handles. It softens the tape and allows me to peel it from the handle or the back of the plates and handles.
Another advisory… I frequently use lacquer thinner to remove leftover traces of permanent marker, but it will attack the ABS handles (as well as some knife handles). Because of this, I will spritz a little thinner to a piece of paper towel so I have complete control of where it’s applied.
Lacquer thinner works really well in removing permanent marker ink. With just enough to wet the region, the marker ink seems to float away.