I've got a couple pair of shorts that are a little snug through the waist. My wife tells me it's because I'm approaching my mid-30's and my eat-whatever-I-want diet is finally catching up with me. I have to disagree. I'm convinced that the shorts have shrank. All my other pants in the same waist size fit fine. Regardless, I just bought some new shorts today and realized that clothes are expensive and I'm not going to throw out perfectly good clothes if I can do something about it.
I've seen waist stretchers that can be purchased online for $15-30, but I decided to try using something I already had. Enter the squeeze clamp. These clamps have reversible jaws that will allow them to "squeeze" inward or "press" outward. You'll also need the "shrunken" clothing, and a medium or large safety pin if the clothing has a fly closure.
Step 1: Prepare the Fly
As mentioned before, if the pants have a fly closure, you'll want to use a safety pin through both layers to hold the closure together to minimize the strain that is put on the button (or clasp) and the button hole while the waistband is being stretched.
Step 2: Commence Stretching
Insert the "stretcher" and apply enough tension to keep it in place. To ease the stretching and reduce strain on everything, it's best to get the waistband wet. This is easily done with the clamp partially tensioned and the pants held upside down over the sink. I used the sprayer at the kitchen sink to spray downward at the waistband, trying to avoid getting any other parts of the pants wet.
Once wet, tension the clamp more to stretch the fabric. Hang the clamp on a hook and let it dey. Once dry, test fit and repeat if necessary. Enjoy being comfortable in your clothes again.
***You want to avoid over-stretching things to the point of seam failure or clasp failure. I didn't need much more room through the waist, so I tightened my stretcher accordingly. It'll require a bit of trial and error. You may need to test fit and stretch again.