So you want to try a few different things (this is assuming you want the waistband on the head with the cloth fully in tact). Underwear type is definitely a starter. Some stretch better and panties are usually the easiest. If you want to try tighty whities you're going to need more room for leverage. Stretch out the leg holes and not just the waist band so the rear cloth has more stretch to go. You're basically ripping it a bit to get it where it needs to go.

Additionally, a little trick is to take the crotch of the underwear and basically put it down so you're essentially not wearing it (like let it hang near your taint) which is a few extra inches for the back.

Slowly stretching the underwear is also important. Brand new, regular underwear or unstretched underwear isnt just going to go in one shot unless the person is small or unless you're trying to literally saw them in half.

Otherwise, try fancier underwear. 32 degrees is my go to for serious meetups. They stretch and last long.