You can tell if your tincture is working by the results. I know plain ol' Vitacost Black-Walnut /wormwood & Black-Walnut tinctures can do the job fine.
You may be expecting to get rid of the critters in a short time and therefore be thinking your products are not effective. It can take months and after that you need to do maintenance for life as their eggs can be everywhere, grocery cart handles, poorly cooked meat, pets, bathroom doors - anywhere.