I have mine set for autoupdate. This only happens if there is NO aircraft picture. If there are local miscodes that I want in my database I make sure there is a picture.
IF I see an aircraft where something looks out of place - eg Flight ID and company don't tie up, no company name, picture and flight id don't tie up, etc and there is a picture then I go to the photo subdirectory and delete the pictures for that aircraft and then click on the aircraft and t updates.
Bit manual but it works for me.
An alternative is to delete all the pictures which will result in every aircraft refreshing but that also has its downside eg - the age old type corruption, etc
A point on the routes - I really think AirNav need to consider the same facility as the aircraft. This is working like a dream. There are also numerous routes that I can see are incorrect or missing on the network but I have correct one on my local database. The route issue is a massive exercise for anyone, auto or manual so the more people that are doing updates the more accurate it will become.