making a clear lcd screen

making a clear lcd screen
Hi, I have been repairing some iPods lately and iPhones, something that is really bugging me is that fact that everytime I finish the job and put everything back together there is a smudge of some sought or a tiny bit of dust or hair. Now I have been using a lint cloth. My question is what spray can I use and what cloth, so the iPod looks as it did before? thanks

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