Hi Stew
I just use a soft nail brush, think it was from elite car care, scrubbed with some weak apc them came up a treat.
From previous experince with machining Range Rover's you might have your work cut out with the PC, as even with the rotary they have prooved to be a challenge in the past, I don't envy you at all when you do it lol.
Paul
Ah well, he's looking at new cars anyway... Won't bother!
Think I need a makita...