I'm not sure what you are asking? Interchangeable focus screens or internal/external cleaning?
For interchangeble screens, there's an add-on I am aware of from Katz Eye. I essentially mimics the focusing screens used in the film days - aka, 100% manual focus, 100% of the time. I considered getting one, but learned instead how to control the AF to get what I wanted.
As for focus screen cleaning, internally, I would use a liquid as absolutely, unconditionally the very LAST resort for cleaning it, with a very sound reason for not sending it in to Canon for cleaning/adjusting/whatever before using a liquid. If it's merely a dust problem, a rocket blower is by far the preferred cleaning method. Do not use 'canned air'. If I were to clean my focusing screen (or sensor, for that matter), the rocket blower would be my first choice. It would also be my second, third and fourth attempts, as well. THEN I would consider a Q-Tip followed by rocket blower. THEN try a lens cleaning cloth...not a T-shirt, etc. If I still wasn't satisfied I got it clean, it would go to Canon as the $100 or whatever to Canon now would be far better than many $$$ for prism and/or sensor replacement from liquid induced problems.
As for the rear of the camera - eyepiece, LCD screen or top of camera displays, rocket blower, then lens cleaning cloth. Nothing else.
