Managing males and pollen is a huge part of breeding. Breeders and growers alike must always take extra care to respect their fellow growers. Pollinating a neighbors flower crop shows a lack of respect for the culture and should be avoided at all costs.
Hemp males can drop pollen from anywhere between 12 hours and 13 weeks after calyx development. Identification of males long before fallen begins to drop is essential. Males tend to grow taller than females and show their sex earlier.
There are several good procedures for containing pollen for selective breeding. It's essential to consider all vectors of possible contamination to and from other male plants. For a small number of males, it is appropriate to remove them from the grow space and into a dry still air space in which you can knock pollen into a container for later use or collect pollen on a piece of paper over a period of days. A window sill is adequate light for a male plant to continue producing pollen. In either case, after each collection wash hands, shower, and replace clothing before approaching any other grow space. Pollen is capable of traveling many miles through the air in large quantities however a more direct vector exists from direct contact by yourself or insects.
The application of stored pollen to flowers should be done with care and timing in mind. Q-Tips are a great disposable applicator. Most seeds take at least four weeks to develop, dependent on the total flowering time of the plant. Pollinated female pistils on the pollinate branch should be labeled especially if multiple male donors are used on one plant. Female plants may also be moved to a safe space for pollination and after a period of 24hours can be washed and returned to the growing space. This is adequate enough time for fertilization to occur. The water renders the additional pollen non-viable. Pollinated branches should receive adequate light and a consistent flowering photoperiod to produce viable seeds. A close eye should also be wary of hermaphrodite flowers which should be plucked or the entire plant removed from the breeding room. Hermaphroditic offspring are indistinguishable from plants produced using male pollen and should never be used in breeding for sensimilla .
For safe open pollination or production of seed, additional measures must be taken to ensure that pollen is contained. Pollination with many males is not selective breeding and is typically only employed after an IBL is established. I have several personal procedures that I employ to ensure that seeds created this way are pollinated with the males intended and that the pollen used is contained.
Firstly filters must be used on both the intake and output of a contained grow space. Whether greenhouse, tent or grow room, air exchange on both ends must be filtered to a degree of at least 10 microns as hemp pollen itself is approximately 25-30 microns in diameter. Cubic Feet Per Minute (CFM) or the airflow of your system must also be taken into account as the air pressure can push smaller particles through a micron filter. Both filters must be replaced often. A bubbler system can also be built to direct pollen into a water bucket with a filter on top. In this way, pollen is collected in the water and the subsequent filter lasts longer.
For outdoor growing clones can always be taken from identified males before flowering and flowered in a contained space indoors. I do not recommend bagging male plants outdoors in an effort to collect pollen. Pollen should be stored without any other plant matter in a container in a dry 25-30 degree space until use.