I just cleaned a Violin over the past few days. Here are the before and after photos. That was a hard job, rewarding though. I is worthwhile to get the instrument serviced ones a year if you are a professional player or a bit less often if you don’t play as much.
Wiping your Violin with a microfiber cloth after playing will keep it cleaner for much longer. Please never user any cleaners not even violin cleaners, they very often make the varnish sticky and so make the dirt stick even more to the violin.