How to Accurately Dose Chemicals in a Nano Aquarium

I have used Seachem’s products in our Fluval Spec V since we built it up.  I love their Prime water conditioner and Flourish Excel for plant growth.  The one challenge to using their very concentrated formulas in a small nano aquarium is accurately dosing in small quantities.  Their suggestion to use the threads on the cap to estimate 1 ml for each thread I find highly inaccurate.  This leads to wasted product and possibly over dosing. I first thought that a syringe would be the best way to meter out small quantities in ml. However, even that had problems