The nice thing with ratios is that you can apply it to any form of measurement. If you have a mini shot glass, you could do 32 of those in water, and fill one up for your 2% chlorhexidine solution. Same with a spoon, a bottle cap lid, almost anything. Just don’t use a large cup because if you end up not needing a full cup of the chlorhexidine solution, then you won’t know how much you actually need. You could also weigh it as well and do it that way.
But for a 2% chlorhexidine solution I do 1:32 solution to water as well. If yours is more concentrated then that, then you’ll need to add more water of course to dilute the solution more.