The tech I used suggested I get my C and Bb. This all relates to the *3 bends.
He suggested I grab my Bb and play a +4. Then bend the .+3 down one step down to the point it sounds like the +4 played on the Bb. I thought about it and I played a clean -3/ on my C. I then play a -3/ until it sounds exactly like the 4 bb. I am no music theory guru but it made sense. I play the +4 Bb then the +3/ until both notes are the same. The math adds up. The +4 was cleaner than the bend but I was able to experiment until both noted were very close and just practiced the -3/ until I could get close or play it. This turned out to be a good exercise to situate my tongue position and play a first step -3 bend on a reputative basis. The second step involved a 5 on my Bb.
Never thought about this but when you practice with two harps that fit this drill hearing the bend played and then trying to replicate makes it easier when you hear the bend right before you try to replicate it. it became apparent I was using too much force and going beyond the -3/. I don’t practice the third step much but the first two on the -3 seem to be by far the most common ones I run across. Hope this helps.