I thought this may be of interest.
I had some specs/smudges on what was narrowed down to be the focus screen. The local photo store recommended sending the camera into Canon (the protect yourself response). I searched the internet and came across this method for removing and cleaning it. I used a corkscrew for the removal but think a dental tool would be a better choice.
Trying to clean it in place is extremely difficult and you cannot use a brush as it seems to just make the situation worse.
It worked wonders for me. Hope it helps
Disclaimer: use at your own risk. 
