Whip Whops
When I bought my recently broken NF 2 years ago, he had absolutely no forward motion at all the the slowest single pace I had ever seen on a horse! In fact I wondered whether he was "all there", he was! He has a wonderful nature and I thought I would give him a try, and the first thing we needed was to get him to move forward without constant leg.
The whip whop was great for this, I have to say I bought a curtain tie back for £2.99 and used the swing the tassel end in his sight but never hit him with it, I did once catch myself though! It has now disintegrated, so I am sure the IH are brilliant, but equally I only used it for a few weeks until he got that walk on wasnt just a joke!
The only thing I would say is make sure that the tie backs dont have hard ridges and obviously look at the issue of them getting caught in hedges etc. they can also be used as a very useful fly swat.
I do feel that as long as it is to reinforce something that they are great and would rather carry that on a younster than a whip. However, everyone has their own opinion and their own horse, I am sure that the sudden movement in some horses would cause a huge leap forward so desensitise first very safely!