Lets face it, shopping with kids is hard. ESPECIALLY thrift store shopping. At least at normal department stores you have a little more freedom to let your child out of the cart or stroller and walk around or play in the dressing room while you try on your clothes. But at thrift stores you can't really do this. They are dirty. And I mean diiiiirtyyyy.
1. Choose to only look at 1 or 2 sections. I used to love spending hours on end combing through every single piece in every single section. That's usually how you find the best things! But that is no longer an option with kids. Now when I go in to a thrift store I usually tell myself that I am only going to look at dresses and shoes or housewares and shirts, etc. This way I only spend about 30 minutes total in the store. I have found that any time after that your kid is definitely done and ready to leave.
2. If you want to look at everything just do a quick scan. This option may take more practice and experience, but try it! Since I have been thrifting for so long I am pretty good at spotting the good stuff just from walking down the isles glancing at the items. I may not find as many great things this way, but it allows me to look at everything in the store. Just keep your eye out for bold patterns or colors in the clothing racks or any fun material or fabric that is unusual and eye-catching.
3. Go when there are little to no crowds. It's easiest to look through a thrift store when you don't have to fight people for dressing rooms, take turns going down isles, or wait in long lines. This also cuts down on a lot of waisted time. Hit up the thrift stores when they open in the mornings and avoid the evenings and weekends. That is when they are most crowded.
And on top of everything else, make sure you have enough snacks and toys to keep your little occupied while you shop. I have found that bringing toys Sawyer hasn't played with in a while really helps because it will keep him interested for longer.
Good luck to all of you and and happy (quick) thrifting!