yeah i hear ya and i gave up on my viewfinder. i've heard the viewfinder screen is user removable but im not messing with it anymore.
Its an easy swap, but unless you get everthing 100% clean the junk will still be there only to show up again. And in time junk always makes its way back in there making the new 25-30 dollar new focussing screen just like your last. I just tore down my 2.5 yr old 50D to do a card reader repair and was shocked how dirty it was in areas. I use my camera though and dont take the care or preventative measures that I should.