Don't give up on DMTs, they can take a joke and are the best lapping stone I've used. Your plate is not ruined. I agree that the continuous-surface 8 x 3" plates do load up during lapping, and can be difficult to clean. The best cleaning method I've found is Barkeeper's Friend liquid, and my fingertips, repeatedly rubbing and rinsing under running water.
Some time back, I switched to using the continuous surface plates for razor honing only, and now use only a big perforated Duo-Sharp plate for lapping (coarse on one side, extra-coarse on the other). The perforated surface really seems to avoid loading up when lapping under running water, and cleaning is far easier because they don't load up in the first place. They can really remove material in a hurry with pressure, but leave little surface scratching when used with light pressure.
I use the big 10 X 4" Duo-Sharp like the one pictured below. They've gotten a little pricey now, but I lucked out and got mine on sale for only $20 more than a regular 8 x 3 plate over a year ago. The big 10 X 4 size really helps. I do x-coarse, then coarse, then move up through 600 grit and 1000 grit wet/dry sandpaper, the sheets laid right on top of the big Duo-Sharp as a base. Works beautifully.
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