I’ve never experimented with growlers, so can’t comment on that. But if you’re still leery about using the 12 oz. bottles that weren’t promptly rinsed, just run to your LHBS if you have one nearby and buy new bottles. You’ll probably pay about 50 cents a bottle, kinda pricey, but then you can rest assured they’re clean and you won’t have any bad bottles in your batch. When I have new bottles I don’t even bother cleaning them. I just submerge them in sanitizer solution and let dry a little right before bottling. They might be a little dusty, but there will be no gunk in them so a thorough cleaning isn’t necessary in my experience.
If you choose to reuse the bottles you have, I 2nd what Loopie Beer said. Submerge them in a PBW or Oxiclean w/water solution and let them soak overnight, then scrub them out well with a bottle brush and rinse with plain water. Sanitize right before bottling (obviously). I have two coolers (and a bottle brush) that I use to clean bottles and makes it a breeze. One cooler is full of PBW/water, the other is full of plain water. Wash in one, rinse in the other. Put them in an empty (clean) dishwasher to dry if you don’t have a bottle tree or fast rack.