It's too late to save the work of cleaning your current pad, but what I like to do is use a single layer wool blanket on the bottom, and then my regular pad on the top. Then I hose off the wool blanket every once in a while while it is still sweaty (or soak it in a plastic tub if it is dry and crusty). I find it a lot easier to wash a single layer wool blanket (like the Mayatex types) than wash the big, stiff, regular pad.
I hate washing the thick ones like you posted a picture of because it is hard to get the dried sweat out of the fleece. And they take forever to dry. The wool blankets dry in 24 hours (in warm, dry weather) and I kind of enjoy washing them. I'm sick, I know!
Plus you keep your thick pads looking like new (if they were clean to begin with).