I realize this isn't exactly an article - but it should be! Revived girlfriend's k-x with the info here from Gerbermiester (post 11 in the thread) - Cleaning up a scratched viewfinder... Also saved an old istDL that I had gotten free because of the damage. Anyway:
https://www.pentaxforums.com/forums/6-pentax-dslr-discussion/39249-scratched-...der-k100d.html
I keep teling people not to clean the viewfinder with a t-shirt or whatever, but...
(anyway, I do understand if I'm eliminated from the contest for not quite following the rules, but....)