I thought about this also. I have only 2 beans left. My germination rate for DDA seeds was 1 out of 3 but 100% since then. Oh well. I'll cross that bridge when i get there.
Mine were 3 for 3 with one mutant.
If only one germs, use the CS and spray one or two lower sites. Put a small fan, like a CPU fan, below her blowing up (stops to imagine the classic Marilyn Monroe image) when pollen drops. Viola! Hundreds of S1 seeds in 4 or 5 weeks. Clean the heck out of your tent/room when done.
If you get both it's up to you. But I recommend selfing each because you don't know if or which purple expression you have until pretty late. I was lucky that both plants were purple flowers and leaves.
I was mainly interested in not having to spray everyday, that's why I tried STS. With STS you can be in coma for 2 weeks and still have success.....
My sick humor is all I have ATM. It's always been my defense mechanism in bad times. Makes for awkward moments sometimes.