you apply colloidal silver or silver thiosulfate to a plant as you flip to 12/12 flower phase, and it will grow pollen sacs. then, just let nature do its own thing.
2 clones is abetter idea. It's still an S1. you'll get a lot more seeds this way as the conversion to male growth is almost 100% early on and timing may not be best otherwise. start them on 12/12 at same time and when you get pollen sacs, it'll pollinate the other plant on its own or you can dust the plant a bit for 1-2 days. that's all you need. Fem pollen isn't as copious as a male plant's production, but even though you don't see it easily, there's tons of it.
check out my "Making fem seeds with STS" diary . i have complete instructions on mixing STS and my trials and tribulations of making first batch of fem seeds.
I do not recommend selfing plant. the garlic storm i selfed was already inbred as fuck, and the selfing just made it a dumpster fire with small yield and inconsistent quality. Much better to find a plant with similar traits and breed them.