Right, so, i'm not going to tell you not to drip acclimate, but I will share some information with you. Full disclaimer, I'm a newbie, but a newbie who has done lots of reading. I would encourage you to do your own research as well. That said:

If you're going to drip, you need to start with water conditioner which detoxifys ammonia. It's my understanding that someting about introducing new air into the bag / container is when the ammonia starts to do it's damage. I've not looked into the specific chemistry so not sure if the gas exchange is what creates the ammonia or if the ammonia is not actually toxic until it begins to oxidize or something. Either way, most will advise you to add a detoxifying water conditioner if you're going to open teh bag and leave the fish in it

Second, you should know that 'drip acclimation' is a pretty big misnomer. Fish can take upwards of a week or more to actually acclimate to water chemistry and conditions. All you're really accomplishing is acclimating the fish to the temperature, and that can be done equally effectively by simply floating the bag/cup.

As a reminder, you should never add the contents of the bag / cup to your aquarium; even if drip acclimating you're going to want to make the final transition by dumping the fish into a net then dropping him into the tank.