Use a sharp paring or petty knife to trim ½ inch from both ends of each grapefruit or pomelo. Reveal some flesh to make removing the peel easier. Then make cuts, from top to bottom and at 1-inch intervals, around each fruit. Make sure the knife goes through the peel and pith down to the flesh. Use your fingers to remove the peel in beautiful, discreet sections.
If the pith is thicker than ¼ inch, wield the knife in a horizontal sawing motion to trim away excess pith from each section of peel. When done, cut each section lengthwise into ⅓ to ½-inch-wide strips.
Put the peels into a saucepan and add enough water so that they float. Cover with a lid or plastic wrap and refrigerate overnight.
Uncover and drain the peels. Return them to the saucepan and again add enough water so the peels float. Bring to a boil over medium heat, let boil for 1 good minute, and then drain. This mellows the harsh flavor of the peels.
To candy the peels, use a wide, high-sided skillet (like a chicken fryer) that can accommodate them in a single layer. Put a wire rack on a baking sheet and place the baking sheet nearby for drying the finished strips. Put the 2 ½ cups sugar and all the water into the skillet. Bring to a boil over medium heat, stirring to dissolve the sugar. Add the peels, lower the heat to a simmer, and cook for 20 to 35 minutes, or until they look glassy and glazed. (If the peels are not all well exposed to sugar syrup, add a little extra sugar and water in a 5:3 ratio of sugar to water.)
Occasionally stir the peels or swirl the pan to ensure even cooking, and lower the heat as needed to prevent scorching. During candying, the plump peels will shrink, straighten out, and soften. The white pith will turn practically clear. Use tongs to transfer each strip to the rack, placing them peel side up and not touching. Discard the sugar syrup or save for another purpose (add soda water for a spritzer, for example). Allow the peels to dry for about 1 hour, or until they feel tacky.
To coat the peels, put the ⅓ cup sugar into a small bowl. Drop in a few strips at a time and shake the bowl back and forth to coat them well. Transfer to a plate and then repeat with the remaining peels. (If you run out of sugar, add more to the bowl.) When all the strips are coated, put them into an airtight container and store at room temperature for up to 7 days.