The way that I wet sand is... (I use the MM pads) I drop the pad into a hospital "spit tray" that is 1/4 full of water and set on an incline to keep the other end of the tray dry.
I flip the pad over and than rub it with my finger to get residue off. Than I put the pad to the plastic. A little time is all it takes, and the water has no chance of drying up, or getting gunked up. When I'm done with one blank, I use a piece of t-shirt to dry the blank and keep the sanding residue from contaminating the next grit.
When I'm done with a certain grit I dunk it in the water again and rub it with my finger to get the grunge off (just like I do at the beginning), and than I stand the pads in the dry half of the spit tray so they can dry and drip into the water.
Hope this was what you're looking for.
Jim