I have a Nikon D5300 that I do not use anymore. I want to give it to my nephew on his birthday. However the viewfinder of the device is very dirty despite the amount of care I put into my gear. I have tried cleaning it with Q-Tips, small cotton slivers dipped in cleaning solution (wringed the excess solution out of it to avoid it leaking into the device). But it still refuses to be cleaned. Any suggestions on how to clean it? It has no warranty so sending it to the shop to be cleaned is no go. Any help?