Which collar, Leash, harness etc should you use to train your dog?

Which collars or leashes do you think are the best to train your dog to walk nicely on a loose Leash?
Lycan and I talk about this subject, okay I talk, he just plods along happily. Also, meet Zara, one of my client's Doggy Walking Dog. She is a very sweet little girl.
#prongcollar #sliplead #clipchamp #germanshepherd #lycan #dogtraining #workingk9 #gsd #dogs #doglover #staffordshirebullterrier #staffies #k9 #looseleashwalking #prong #collar #leashtraining #harness #checkchain

[@AdventureswithLycanmyGSD]

So what do you think? Should you rely on a particular collar, leash or harness for proper loose leash walking? Would your dog understand what they are supposed to do if you use these only?