In this class, I don't remember at what point though, Rabbi Mizrachi mentions that one receives reward even for encouraging someone to upgrade their tzitziot from cotton to wool. He says that according to most opinions wool is preferable to use. Like most things there are arguments and according to some, cotton is equally as good and even preferable in some cases. Rabbi Mizrachi himself mentioned in a different class (I don't remember which) that the Steipler Gaon made it a point to wear cotton tzitzit to demonstrate that the rabbinical commandment supercedes a Torah commandment! Just to show you how halacha is dynamic.
In any case, he says that even encouraging someone to a mitzvah behiddur, i.e. beautifying it, or keeping it on a higher level, accrues reward for the person who motivates the other to do so. The same would apply to upgrading one's mezuzot from a basic quality to a higher quality.
We launched this blog and project to encourage more people to learn about and keep the mitzvah of tzitzit. If you want more information or to help us do so, please contact us here for different ways to help! There are so many possibilities, and by encouraging someone to wear tzitzit, you get a spiritual dividend for every second he wears them!