How to save and store pollen
This depends on the plant species. Some pollens can be dried and frozen for lengthy periods, other pollens do not survive for more than a few hours (or less).
Binucleate pollen (pollen with two nuclei) can often be stored more easily than trinucleate pollen (with three nuclei).
The most important factor for freezing pollen is that it is dry. Next is the temperature and for most typical home freezers the temperature of 0F or about -18C is fine.
Sometimes frozen pollen can only be thawed once and then the remaining pollen is no longer viable and should be discarded.
Pollen can be saved on Q-tips or cotton or dry anthers and may simply be stored in small airtight containers in a freezer.
Pollen of some species will keep for several days at room temperature and other pollens may keep for longer periods at normal refrigerator temperatures.
It is best to experiment with the pollen by freezing it for a day and trying some test crosses.