Mexican bird of paradise produce seedpods during the summer. The seeds may be collected and germinated to produce new plants.
The easiest way I have found is to take your seedpods and place them in a dryer bag with a zipper on it. I hang mine outside for a couple of months and allow the local weather to assist in splitting my seed pods for me.
When the pods split a good majority will start to curl and trap your seeds. You will need to take open the curl with the tip of another seed pod in order to release your seeds.
This bag of seeds is off of two of my bushes that are around 3 years old now. As you can see there is plenty to share with neighbors and other gardeners.
Once you are ready to plant your seeds you will need to sand or abrade the outside of the seed to remove the shine and make the seed coat thinner. You can use sandpaper or a fingernail file.
Next you can place in water overnight or boil some water and drop the seeds into the hot water for about three minutes. Then add cold water to drop the temperature of the water to around 110 degrees Fahrenheit and let the seeds sit overnight. The seed coat and membrane will peel off and you can plant the seed in potting soil. New plants should emerge in about a week. Do not over-water or the seed may rot.