With a vegetable peeler, peel off long sections of grapefruit peel, leaving behind the white, bitter pith. When you have peeled the whole grapefruit thusly, cut or tear the peels into small pieces between 1" and 1.5". Boil for twenty minutes. Drain off the orangey water. Boil for twenty more minutes. Drain. Boil for twenty more minutes. Drain.
NOTE: Do not allow the grapefruit-infused steam to get into your eyes as you drain. This warning was NOT in the recipe I found.
Set aside the limp, steaming grapefruit peels. Boil 1 1/2 cup of sugar in 1 cup of water. Stir so that the sugar is completely dissolved. When the sugar is dissolved, add back the grapefruit peel. Reduce heat to a simmer. Stir very often for about 40 minutes. Near the 40 minute mark, you'll notice that the sugar is starting to recrystalize. When the sugar is no longer easily scraped off the side of the pot with the wooden spoon you've been stirring with, you're done.
Dump out the candied grapefruit peel onto waxed paper. Separate all the pieces carefully (they're hot!) and let cool and harden.
Time-consuming, but amazingly easy.