I did your research for you:

Firebush aka Hamelia patens - root in water or moist soil or soil layering.

Kentucky coffee tree aka Gumnoclades dicora - propagated by root cuttings or by seed.

Fakahatchee grass aka Tripsacum dactyloides - divide clumps in springtime.

Beach sunflower aka Helianthus debilis should be propagated by cuttings - take 4-inch stem cuttings any time of the year, remove all but the two terminal leaves and stick in slightly moist potting soil. Cuttings should readily root without any rooting compounds.

Sea Grape aka Coccoloba uvifer - propagation by seed or ground-layering.

Beach sunflower will readily re-seed. It tends to get old and woody pretty fast. At that point I would pull the whole plant up and there were always new seedling to take it's place.
Fakahatchee grass will re-seed to a lesser extent just keep you eyes open. Same with muhly grass.
You might want to post over on the exchange page for seeds. there are plenty of people who grow natives and have seeds...but you have to have something to trade for.