I have a very irritating issue with my Canon 40D bought only two years ago: the shutter release is working only 1 times over 4 tries. After some google searches I found this solution: pour one spoon of isopropyl alcohol in the battery compartment while keeping the camera up-side down and pressing the shutter release a few times, then wait until alcohol is completely evaporated.
My question is: is this method safe, reliable and useful?
I have been able to find only answers about external use of alcohol, but not internal.
My secondary questions are: if it works, how come? Is the liquid just flowing through the mechanism and then enters in contact with the dirty pieces? What kind of dirt lies at the origin of this issue, and most importantly how can I avoid this to happen again?