How do you clean your instrument?

For strings, I use alcohol swabs. No chance of alcohol seeping through any cloth, but I do still put a cleaning cloth over the body of the violin just in case I drop the swab. Don't quote me, but I'm pretty sure alcohol doesn't affect the fingerboard. Or at least it doesn't affect mine, and I use a swab to clean the fingerboard every once in a while.

For the violin body, I would really consider leaving it your luthier, but I like the Psarianos cleaner/polish. It's good for maintenance, but I would still bring it to my luthier if it needed a deep cleaning. I only use that cleaner once every blue moon. You probably don't want to use any cleaner regularly. Just use it to see you through to the next time you take it to the luthier. Lots of people like the hill cleaner, but I wasn't a fan of it.

Hows sad, that the Murphy's had such and effect on your violin's body. I would never use any liquid or paste on my violin.

I find that terry cloth, like a washrag (dry), works well to remove rosin from strings. As for the body, I lightly use a microfiber cloth after every use. Avoid using terry cloth on the violin's body, as it can catch on spurs or splinters.

I occasionally, and sparingly, use peg dope on the pegs, to make them smoother to adjust.

How do you remove those white lines on the fingerboard underneath the strings ?

https://www.youtube.com/watch?v=v7MIWngBpA8

There's a topic list with timings if you expand the text description, Ryan includes a nice tip on installing strings in such a way as to make it easier to position the pegs for ease of turning/tuning.