The easiest way to achieve the results desired are as follows.
1 chose location for seed production, branch or flower.
2 mist plants flowers, excluding the desired flowers selected for seed,
3 bag the missed plant, again excluding the desired seed production sites.
4 dust with pollen, paintbrush works.
5 allow to hang out and dry a bit, 1-2 hours, then spay the whole thing with water again
done
The water activates a trigger within the pollen when wet stopping it from fertilizing. I have done this many times with great success.
Peace