I clone my bottom two branches and treat them with homemade CS as the mother matures. You want to hit one of the upper very healthy branches with this pollen so there is a sacrifice but a return on your investment. At $10 a seed average, give or take, and you end up with 200 more seeds... It's worth it!
You just harvest your buds around the pollinated bud and leave that one to ripen those seeds. I mark mine with a bread tie.
It seems like auto's were made for CS treatment using this method. The clones start to flower immediately. This way you can start your reversal immediately as well. Roots aren't really even necessary in the beginning. I have never tried doing this outside of my Aerogarden however, and doubt it would work in soil. I feel it would take too much time where hydroponic setups greatly pick up the growth pace. A great place to look for cheap Aerogarden's is Ebay. Many people get them as gifts and then sell them used after they have grown the initial seed kit included with it. This makes me do cartwheels haha
Here's a link to my thread on how I do it:
https://www.autoflower.org/index.php?threads/aerogarden-cs-sex-change.27412/
I apologize it is a somewhat long thread. This was my first attempt and I have changed nothing in my future reversals.
The key is to take those bottom two clones ASAP, as soon as they are large enough. This is a tortoise and hare race.
I too am wondering about pollen storage however. I am currently starting another World of Seeds Northern Lights X Big Bud in hopes of hitting her with my Spliff Seeds White Widow pollen that I stored some time ago. This would be feminized breeding.
For what it's worth I store my pollen the same way I store seeds for the most part. I take the pollen and place in small "lip gloss" jars that you can buy on ebay for very cheap. Pollen must be DRY DRY DRY! Then I place my containers in a clean glass jar with a hand full of dry white rice on the bottom, all are then refrigerated. The seeds are stored the same way but in their packs instead. The seed I just started is well over 2 years old and sprouted around 24 hours after placing in paper towel. I am confident the pollen stored in the exact same manner will be as viable. Time will tell I guess!