imho you only need to clean the beer line and tap internals (not including the spout) when you change the keg.. pubs will do a weekly line clean but may have changed barrels more frequently.. while your corny has kept a sanitary seal from your keg upto the tap seal since installed, very little chance of anything nasty not already there getting in... unless your chopping and changing a lot ??
The tap spout however can harbour all sorts of nasties, beer and air mixed..but a squeezy bottle of warm water rinses that out after a session., even better if they unscrew you can just use the tap to rinse em,...
just clean the line and tap thru with the cleaner and steriliser you use in the keg youve just emptied befor using it again or storage :)
However if you have a need to clean the lines mid keg for any reason a pump action garden sprayer can be used to pump fluids about, but if ussing one i would dedicate it to the task..