The problem I had was with the trackpad button, either it would not respond or would require much force, and or it would respond multiple times with one push.
My Mac is a Powerbook G4 Aluminum, 15" 1.67 GHz. I used your instructions for removing the keyboard. I located the the printed circuit ribbon leading to the trackpad button. I removed the 2 phillips screws holding the button to the keyboard. I folded the ribbon over and was able to see the trackpad button. The button seemed to have 4 small openings where it was soldered to the printed circuit ribbon. I thought I could spray some contact cleaner into those openings. I first tape off the area so as not to effect other components. I sprayed the openings with a TV tuner spray that contained 1,1,1 Trichloroethane. I am not sure this chemical is allowed in California any more (something I acquire about 25 years ago). I continually activated the button and wipe off the excess spray before I reassembled the laptop. As far as I can tell the spray did not effect the other components and the trackpad is working fine at this time. I worked very slowly since this was the first time I had taken my Mac apart (about 3 hours of work). Sorry I did not take a photo.
Make sure the spray you use does not have a detrimental effect on the other components.