So, I inherited a treasure trove of old transparencies from my grandparents' extensive world travels in the 70s. Unfortunately, these are pretty dirty, covered in spots and whatnot. I plan on scanning these and doing some touch up in PS, but what is the best way to pre-clean them to try to ease my post-processing workload? Also, any tips on scanning transparencies with a Canon 8800 scanner for best results? Thanks.