I use PBW on my carboys; I mix according to the recommendation on the bottle and then let it soak overnight. In the morning I dump it out and it takes all the caked on hop and yeast trub with it, works like a charm. I imagine it would work very well for bottles as well, although it probably wouldn’t be very cost effective. IMO it’s best to use some dish soap, shake the heck out of it for a few seconds to get anything off the bottom, and make sure you sanitize before bottling. I had a few bottles I got from a friend with some mold growing on the bottom so I had to use a bottle brush and then an overnight bleach soak, but I’ve only ever had to do that once. It all depends on how much elbow grease you’re willing to put into it! PBW would definitely = quicker and easier, bottle brush and elbow grease = cheaper.