Dressage whips often have too much movement in them. You tap once, but they slap back for another tap sometimes, and this hurts precision. However, they are perfect for more advanced moves, but for a beginner something more heavy and stiff, and with not that much of a "bite" is sometimes better.
I prefer these - Reitstick Set für Natural Horsemanship | eBay
Made after the merchandise of the NH clinician Honza Blaha. They are lighter and shorter than most "carrot sticks", swift and with a nice bite, if it is neccessary. I use a good dressage whip just as well, but these sticks have the perfect weight/lenght ratio for me as an individual.