alexey75 wrote:
Is it necessary to open the drums and clean it?
If yes, can I open the drum and spray all parts with brake cleaner?
What is more important is re-packing the bearings !
To do it correctly, you need to remove the brake drums and that will give you a chance to inspect the brakes. Dirt is "normal" and I would not spend a lot of time cleaning unless the shoes need to be replaced.
Simply spraying a whole can of brake cleaner on each will NOT make them "squeaky clean". You would have to disassemble and use a wire brush. There are also a few point behind the shoes that need lubrication and brake cleaner would remove that.