The way I feel I use the left tongue to pronounce the "B" sound is difficult for me. I was practicing it while pushing my wife in a wheelchair a couple of weeks ago. It feels like it takes a lengthening and relaxing of the left tongue while softening the left cheek by the left lips. In order to do it efficiently I found myself shifting my pelvis minisculely to the right and lengthening my left torso. I then started pushing my wife up one of the small hills (incline may be a better word). Usually my left ankle hurts slightly with the effort just below the lateral malleoli. There was a totally different sense of my ankle. It did not hurt and felt strong and functional. We have gone on many trips since and once in a while I get the same ache but my usual is now the opposite. It feels like it is in the right (should I say "left") place.
Yeah Baby Yeah
Just an additional thought. Playing with the left tongue has come very slowly. A little shoot here, a period of nothing, then a bud with a very small flower but no where equal to what I do with my usual right tongue. It still feels like it is developing.