Ditto on both of the above. Actually, I have used a piece of apple, but not tried an orange peel.

Put a piece of orange peel or apple wedge in the jar/bag overnight. I haven't had to do this for awhile since I store my brown sugar in a jar and maybe just use it fast enough.

I microwave it for 10 seconds at a time until it is granulated. I also store in a ziplock bag placed into a plastic container, and it stays fresher longer.