Brian, most citrus nurseries purchase their rootstock seed from large companies that maintain groves of trees for the various types of rootstock seed that they market. Following is the procedure that is commercially used by major companies that market Poncirus Trifoliate seed. You can adapt from this. The process of producing large volumes of rootstock seed includes harvesting the fruit at normal maturity, crushing the fruit in water, stirring the resulting mixture with pectinase enzymes at specified temperatures to separate the seed from the pulp, and washing out the seed. The washed seed has its surface sterilized with 125-F water for 10 minutes, then dipped into a 1 percent solution of 8-hydroxyquinoline sulfate (8HQS), then left to air dry on screens in the shade, and packaged in plastic bags. When storing, it is important to leave these storage bags open initially until the seed equilibrate with the refrigeration temperature. If the bags were closed before refrigeration, the undissipated heat and humidity may generate condensation inside the bags which promotes fungal pathogens. Fresh used citrus seed has the highest germination percentage, however seed can be stored at 40-F for as long as 6 months with little loss of viability. Seed stored at room temperature looses viability quickly. NOTE: 8-HQS is just a common bactericide, if you can't locate it, there are a lot of bactericides that can be used. Be sure that the medium that you plant the seed in, and the seed tray used are completely sterile . Nurseries that purchase the seed and grow them out add dolomitic limestone to the seedling medium to maintain a pH of 6 to 7, plus controlled slow release fertilizers with micronutrients. The seed is planted 1/2 inch deep. Humidity maintained between 80 and 90%, temperatures are kept at 85-F. Germination is further enhanced by pealing away the testa (outer seed coat). Germination is further enhanced if the seed trays can be heated from the bottom to maintain the 85-F temperature in the media. Following the above procedures seedlings 2 inches tall with three leaves can be achieved within 10 to 14 days after planting, though it can take as long as 40 days for all the seed to germinate. - Millet