Not sure why you treat inverts differently than fish. Also don't know if you're getting them from your LFS or online. Reef Cleaners will not guarantee inverts if you drip acclimate them. They say that being closed up for a day causes ammonia to spike and opening the bag makes it worse so leaving the inverts in the shipping water while dripping causes more harm than putting them into the tank after floating with the bag still closed to even the temperature.
Hmmn, doesn't really make sense to me. All of the places I buy inverts keep them at 1.024/25, which negates the need to drip them. Fish, on the other hand, come in all over the place, as low as 1.015. I don't drip them either because I adjust my QT, but if I didn't I'd be inclined to do some kind of salinity acclimation.
I drip my inverts because I run a "dirty" tank and usually don't want to run the risk. For example, when I got my sea apple and my slug, I wanted them to drip because if they got stressed then my whole tank is gone.
As far as obtaining, I have my lfs special buy them so I don't have to pay shipping