Man, I feel your pain on that $9 powder letting you down, nothing stings quite like a cleaner that costs real money and does nothing. I have a mug with a hairline crack near the rim too and the stain in that line is stubborn, so I get why you're asking. In my experience the baking soda paste helps a little on the surface of the crack but it won't pull the stain out of the inside of the line, your mileage may vary though. Take it with a grain of salt since I haven't tried anything stronger than a toothbrush on mine.

Man, I used to roll my eyes at enclosed quotes and think people were just burning money. Then I watched a guy hand wash his Chevelle before loading it and it kinda clicked, some cars just deserve the extra care.

Grabbed my book and walked to this tiny park near the hostel when the same thing happened to me in Porto. Sat on a bench for like 3 hours just people watching, old guys playing cards, kids kicking a ball around, a lady selling fruit from a cart. Ended up talking to this guy who ran the corner store and he told me where to get the best cheap lunch. Honestly it turned into one of my favorite days of the trip and I never would've left my room otherwise. Now I kind of hope the wifi breaks sometimes.