First you have to get seed! Hibiscus are not true to seed. That means, when you harvest seed from a plant, the seedlings will not have the same characteristics as the plant from which the seeds came. Odds are the plants from seed will look entirely different than the mother plant! That's what makes hybridizing Rosa-sinensis exciting. Bloom of the hibiscus hybrid cultivar named "All Aglow"
First you need some pollen. Take a close look at this bloom. There are five bright orange stigma pads located on the tip of the pistil, behind the pads are the pollen sacs. On this bloom, the pollen sacs have not opened yet. Not a good candidate to pollinate another flower yet but it is a good one to pollinate with another flower. You want to look for bright orange powdery pollen like the pollen on this bloom...
Then you take the flower with the pollen and rub the pollen onto the stigma pads of the other flower... You will see the pollen sticking to the pads..
Another example... Now you have hybridized a hibiscus! Then I tag the bloom with what I crossed it with. If it is a dry or sunny day, it is a good idea to mist the flower.
The flower will fall off leaving the ovary behind. Sometimes if it didn't take, the flower and the pod will come off together!
I like to wait a few days to see if the pod stays on the plant, and if it seems like it is not going to abort, I put an organza bag on it to protect it from pests. A lot of people like to remove the calyx (the little leaf-like parts next to the seed pod) because pests like to hide in there! It takes about two months for the seed pod to mature, at any point it could abort and fall off if the pollination was not successful.