Found out there are numbers of stubborn dusts stuck on the upper side of the focusing screen of my Pentax K-30. It just won’t go away by vibrate the camera body or using blower to blow into that area. After done some search and read through Pentax Forums‘s thread, i decide to take it out and clean it.
#5 Do mind that bottom side of Pentaprism and mirror are now exposed, i cover it up to avoid more dust into it.
#6 Check the screen under a bright light or hold the focusing screen to the light to double check cleanliness. Reverse the process to install it back. Your focusing screen position will be exact same as image above, note the extra part is on the left hand side.
Do look through viewfinder by turning on the camera, mount any lens on it and focus on a white background. Check whether there are amount of dust remain, if it is acceptable and doesn’t disturb composing then you are good to go.