Poison Spit adds poison counters to other players. If I run out of poison counters, can I keep giving them, ie use other tokens to represent them?
The rules don't cover this, so you have to decide as a group. However, my advice is that there's no reason running out of tokens should limit the effect. You wouldn't run out in a 2-player game, so why should you run out when there are 6 players? If you have to give out 5 tokens and only have 3, how do you decide who gets one? The simplest solution is, as you said, just use something else to track them.