In south Florida, Nitidulid beetles pollinate Rollinia and true Annona species. Bigger beetles and bull ants appear to pollinate Guanabanus species [soursop and related species]. Carrion flies pollinate dark-red-petalled Asimina species.
Encourage presence of Nitidulid beetles, which are only a couple of millimeters long, by allowing fruits, especially citrus, to to be available to the beetles as the fruits rot on the ground.
I have never seen, nor heard of, any species of bee pollinating any Annonaceae.