My local outdoor pool has a chin-up bar (as part of a deployable multi-gym thing), but because it has to survive the elements, it's just a plain galvanized steel bar. The bar is less than an inch in diameter, so I can easily wrap my fingers around it.
Usually, such bars have rubber on the outside, or knurling, so that you really have to be sweating a lot before they become slippery. This one is completely smooth. When my hands get even a little sweaty, it becomes slippery, and I worry I'm going to lose my grip on it. Can I improvise something to cover it with to avoid slipping? It has to be something I can easily take with me, and remove when I'm finished. My towel is the obvious thing, but it would grip my hands well but still slide over the bar.