I beginning to sound like a broken record LOL but I think one of the problems is the advent of these one day courses in massage. Done well it can be effective but far too many courses do not cover more than just a basic routine. One day is simply not enough. There is no underpinning knowledge, no understanding of what you are trying to achieve and how to achieve it. While nice, too often it's not effective.
I do a lot of corporate work and IHM does not compare to the acupressure chair massage. 95% of people want chair massage, the remaining go for reflexology and handful give IHM a try, but most tend go back to the chair massage.
Back to the original question, I prefer to use a low back chair rather than a stool as it provides some support for the lower back although one of the advantages is that a suitable chair can usually be found in most workplaces/homes.