I would like to get a spare rear subframe shot blasted and powder coated...As for now, I remove arch linings and removed all the collected mud/leafs/twigs from behind them and give the arches a good scrub/rinse/dry... Sad I know...
I removed a front arch lining recently and found nothing at all behind it. It was clean as a whistle! I suppose it depends on how manky the roads are in your area.