Enkay - Extra Fine All-Purpose Blue Polishing Compound (1LB)

Q: can this be use to polish the headlight lense, if not do you have a recommendation?

You can use on headlights. I use high speed buffer with speed control to slow the pad down as not to generate excessive heat. Start buffer and press the hard compound bar against the buffer pad. Holding it against the pad heats and softens the bar so the compound loads in the buffing pad. Then ever so lightly buff the headlight with the pad. A word of warning. To much pressure against the headlight will melt the plastic lense. Never hold the pad in one place. Continually move the pad across the plastic lightly.

Q: Can this be used on a stone sink before application of sealant?

It's usually used for last step for polishing metal to its highest finish. Not sure about stone. In theory yes.

Q: The bar appears dry, crumbling, and does not stick as other greasy bars. Is there a way to restore its consistency?

I could be wrong, but some bars are like this depending on the compound and has just dried out. Most times, I just add some water when I'm polishing a metal and make a paste or slurry or whatever consistency needed...sometimes I even use it almost entirely dry. I put a felt pad on my dremel and turn it on, pushing the tip into the bar which heats/melts the paste into the felt. :)